Brent Fultz, California Institute of Technology
Giulia Galli, University of California Davis
Malcolm Guthrie, Carnegie Institution of Washington
Chi-Chang Kao, Stanford Synchrotron Radiation Lightsource
Symposium Support Efree, a DOE-funded Energy Frontier Center
DDD2: Electronic Structure and Dynamics
Tuesday PM, April 02, 2013
Marriott Marquis, Yerba Buena Level, Nob Hill AB
2:30 AM - DDD2.01
High-pressure Synthesis and Physical Properties of the Mixed-valence Chromium Oxide K2Cr8O16
Masahiko Isobe 1 Yutaka Ueda 1
1Institute for Solid State Physics, Univ. of Tokyo Kashiwa JapanShow Abstract
The hollandite-type chromium oxide K2Cr8O16 has been synthesized under high-pressure/high-temperature conditions with cubic anvil type apparatus at 6.7 GPa and 1273 K. In the crystal structure, the double chains of edge sharing CrO6 octahedra share corners with neighboring chains to form a Cr8O16 stoichiometry framework that encloses large four-sided tunnels. The K+ cation is located in the tunnels.K2Cr8O16 is a mixed-valence compound. The formal oxidation is Cr+3.75 , since the crystallographic site of chromium atom is unique. Combining electrical resistivity, magnetic susceptibility, and x-ray diffraction, we found that K2Cr8O16 is a ferromagnetic metal with Tc = 180 K and shows a transition to an insulator at 95 K retaining ferromagnetism. The metal-insulator transition of K2Cr8O16 is quite unique; it has a metal-insulator transition in a ferromagnetic state and the resulting low temperature phase is a rare case of a ferromagnetic insulator. In the low-temperature ferromagnetic insulator phase, almost the same Cr-O bond lengths for the four Cr sites indicate no charge separation/order. The observed structural characteristics well coincide with the Peierls mechanism for metal-insulator transition proposed from electronic structure calculations. The Peierls mechanism in a system of fully spin-polarized electrons is indeed a very rare phenomenon.
2:45 AM - DDD2.02
High Pressure Low Temperature Studies on 1-2-2 Iron-based Superconductors Using Designer Diamonds
Walter O. Uhoya 1 Georgiy M. Tsoi 1 Samuel T. Weir 2 Athena S. Sefat 3 Mitchell E. Jonathan 3 Yogesh K. Vohra 1
1University of Alabama at Birmingham Birmingham USA2Lawrence Livermore National Laboratory Livermore USA3Oak Ridge National Laboratory Oak Ridge USAShow Abstract
High pressure low temperature electrical resistance measurements were carried out on a series of 1-2-2 iron-based superconductors using designer diamond anvil cell. These studies were complemented by image plate x-ray diffraction measurements under high pressures and low temperatures at beamline 16-BM-D, HPCAT, Advanced Photon Source. A common feature of the 1-2-2 iron-based materials is the observation of anomalous compressibility effects under pressure and a Tetragonal (T) to Collapsed Tetragonal (CT) phase transition under high pressures. In addition, antiferromagnetic magnetic phase transitions were observed at low temperatures and followed to high pressures in these samples. Specific studies on Ba0.5Sr0.5Fe 2As2 and Ruthenium-doped BaFe2As2 samples will be presented to 10 K and 40 GPa. The collapsed tetragonal phase was observed at a pressure of 13 GPa in Ba0.5Sr0.5Fe2As2 at ambient temperature. The highest superconducting transition temperature in Ba0.5Sr0.5Fe 2As2 was observed to be at 33 K at a pressure of 5.6 GPa. The superconductivity was observed to be suppressed on transformation to the CT phase in 1-2-2 materials. The structural and magnetic phases will be correlated to the superconducting region observed under high pressure and low temperatures.
3:00 AM - DDD2.03
Understanding the Charge Reservoir Layer in Mercury Based Cuprates Using High Pressure X-Ray Spectroscopy and Scattering
Shibing Wang 1 2 Wojciech Tabis 3 Ku-Ding Tsuei 4 Mun Chan 3 Wendy L Mao 1 2 Chi-Chang Kao 3 Martin Greven 3
1Stanford University Stanford USA2SLAC National Accelerator Laboratory Menlo Park USA3University of Minnesota Minneapolis USA4National Synchrotron Radiation Research Center Taiwan TaiwanShow Abstract
Understanding the physics of high-Tc superconducting cuprates represents a long-standing problem in condensed matter physics. The interaction within and between the copper-oxygen sheets and the charge reservoir layers represent key components in controlling Tc. Both chemical doping and pressure can dramatically change transport properties by tuning the structural and electronic configurations. We report Hg L-edge x-ray near edge spectroscopy (XANES) and resonant inelastic x-ray scattering (RIXS) studies on HgBa2CuO4+δ (Hg1201) with a variety of doping levels and at different pressures. Hg L3-edge XANES are collected in partial fluorescence yield geometry to obtain high-resolution spectra, and are shown to have strong polarization dependence for single crystal Hg1201. Together with their known structural and Tc dependence with pressure, this study provides insight into the mechanism of high-Tc superconductivity in the Hg-containing cuprate family.
4:00 AM - DDD2.05
The Ferromagnetic-antiferromagnetic Phase Transition in CeFe2: Tuning Magnetic Competition at High Pressure
Rafael Jaramillo 1 Yejun Feng 3 Jiyang Wang 2 Jasper van Wezel 3 T. F Rosenbaum 2
1Harvard University Cambridge USA2The University of Chicago Chicago USA3Argonne National Laboratory Argonne USAShow Abstract
Magnetism in rare-earth inter-metallic compounds is essential for many established and emerging technologies, and understanding the mechanisms by which magnetic ground states are selected and stabilized has long been a mainstay of materials physics. The drive to find alternatives to strategic rare earth metals in permanent magnets adds to the relevance of this problem. CeFe2 is a Laves phase rare-earth inter-metallic magnet with a ferromagnetic ground state, and it can transformed into an antiferromagnet by tuning through a magnetic quantum phase transition by chemical substitution (e.g. Ce(Fe1-xCox)2). The arrangement of magnetic interactions - the microscopic magnetic Hamiltonian - that stabilize both ferro- and antiferromagnetic ground states in this material has long been a mystery.
Here we use magnetic x-ray diffraction from stoichiometric CeFe2 single crystals in a diamond anvil cell at high pressures and cryogenic temperatures to extend the phase diagram along the pressure axis . We confirm by direct measurement that the ferro-to-antiferromagnetic quantum phase transition can be driven by pressure as well as chemical doping. We find that the magnetic phase transition is accompanied by a rhombohedral distortion of the lattice that creates two inequivalent Fe sites with different magnetic environments. By combining our magnetic x-ray diffraction data with symmetry analysis and numerical simulation we deduce the microscopic magnetic Hamiltonian. We find that the dominant magnetic interaction is antiferromagnetic coupling between Fe and Ce sites, and that this interaction remains satisfied in both ferro- and antiferromagnetic phases. The phase transition is instead driven by competition between the sub-dominant Ce-Ce and Fe-Fe interactions, and one set of interactions is always frustrated.
Our results underscore the value of high pressure as a tuning variable that allows us to disentangle the roles played by lattice spacing, symmetry, disorder, frustration, and competing interactions in determining the overall phase diagram. The resulting model of frustration being shifted between sublattices may serve more generally for understanding magnetism in Laves and other pyrochlore-related inter-metallic magnets
 Wang et al., Pressure tuning of competing magnetic interactions in intermetallic CeFe2, Phys. Rev. B 86, 014422 (2012).
4:15 AM - DDD2.06
Pressure Induces Magneto-resistance in LaMnO3
Maria Baldini 1 Viktor V.V. Struzhkin 2 Lorenzo Malavasi 3 1
1Carnegie Institution of Washington Argonne USA2University of Pavia amp; INSTM Pavia Italy3Carnegie Institution of Washington Washington DC USAShow Abstract
During the past decade, the high pressure driven insulator to metal transition (IMT) in LaMnO3 has been widely investigated. In particular, the origin of the transition and the role played by electron-electron and electron-lattice interactions have been the subject of a large number of experimental [1-3] and theoretical [4,5] studies. Despite the considerable efforts, the key question of whether LaMnO3 is a classical Mott-Hubbard insulator or not remained unresolved.
We performed high pressure Raman measurements up to 34 GPa over several low temperature cycles which provide the first evidence for persistence of the Jahn Teller (JT) distortion over the entire stability range of the insulating phase . This result conclusively resolves the ongoing debate, demonstrating that LaMnO3 cannot be considered a classical Mott insulator.
Evidence for the formation of domains of JT distorted and symmetric octahedral was found from 3 to 34 GPa suggesting that LaMnO3 enters the metallic state when the fraction of undistorted octahedra domains increases beyond a critical threshold.
This result also has broad implications for understanding the behavior of manganite systems. The importance of inhomogeneous and competing states was recently found to be fundamental for describing colossal magnetoresistence effects in hole-doped manganite compounds . In this context, it is interesting to consider whether or not the colossal magneto-resistance effect may be induced in an undoped sample as LaMnO3 by applying P. To verify this hypothesis, high pressure resistance measurements have been performed as function of temperature and magnetic field. Evidences of colossal magneto-resistance effects have been observed at 29 GPa, when LaMnO3 is entering the high pressure metallic phase. Transport measurements performed up to 34 GPa varying the magnetic field from 0 and 8 T will be presented.
 I. Loa, et al., Phys. Rev. Lett. 87, 125501 (2001).
 A.Y. Ramos et al., Phys. Rev. B 75, 052103(2007).
 A.Y. Ramos et al., J. Phys. Conf. Ser. 190, 012096 (2009).
 A. Yamasaki et al., Phys. Rev. Lett. 96, 166401 (2006).
J. D. Fuhr et al., Phys. Rev. Lett. 100, 216402 (2008).
 M. Baldini et al., Phys. Rev. Letter 106, 066402 (2011).
 J. Tao et al., Phys. Rev. Lett. 103, 097202 (2009).
4:30 AM - DDD2.07
Sustainable Superconductivity at More Than Doubled Ambient Critical Temperature in Ba1.5Phenanthrene
Xiao-Jia Chen 1 Takaki Muramatsu 1 Wenge Yang 1 Viktor V. Struzhkin 1 Ho-Kwang Mao 1 Zhen-Xing Qin 2 Adam Berlie 2 Hui Wu 3 Qingzhen Huang 3 X. F. Wang 4 J. J. Ying 4 P. Cheng 4 Z. J. Xiang 4 X. H. Chen 4
1Carnegie Institution of Washington Washinton USA2Chinese Academy of Sciences Hefei China3National Institute of Standards and Technology Gaithersburg USA4University of Science and Technology of China Hefei ChinaShow Abstract
Exploring superconductivity at higher transition temperatures Tcs in light elements such as hydrogen and carbon and their organic compounds has long been an attractive issue. Cation-doped aromatic hydrocarbons have been discovered to be superconductive with an increasing Tc by adding more hydrocarbon rings. Here we present a discovery of an enhancement of Tc from the ambient 4.8 K to 12.2 K in compressed Ba1.5Phenanthrene by magnetic susceptibility measurements up to 61 GPa. In contrast to the existence of superconductivity within a very narrow pressure range in fullerides, we find that this organic compound maintains superconductivity at more than doubled ambient Tc even at 61 GPa. A phase transition in the region between 3.0 and 5.4 GPa and an orientational disorder at around 28 GPa are identified using synchrotron X-ray diffraction technique. A nice correction between Tc and the angle between two crystal axes of the monoclinic unit cell over the whole pressure range studied indicates the unconventional nature of superconductivity in aromatic hydrocarbons.
This work was supported by the EFree, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.
4:45 AM - DDD2.08
Pressure Induced Structural Transitions and Metallization in Ag2Te
Zhao Zhao 1 Shibing Wang 2 3 Haijun Zhang 1 Wendy L. Mao 2 4
1Stanford University Stanford USA2Stanford University Stanford USA3SLAC National Accelerator Laboratory Menlo Park USA4SLAC National Accelerator Laboratory Menlo Park USAShow Abstract
Ag2Te is known as a superionic conductor, a good thermoelectric material, and by recent calculation a new binary topological insulator with a highly anisotropic single surface Dirac cone. At ambient pressure and room temperature, it forms the monoclinic structure with space group P21/c (β-Ag2Te). Constituted of non-magnetic atoms, nonstoichiometric β-Ag2Te has unusually large and nonsaturating linear magnetoresistance, which makes it an attractive material for producing megagauss magnetic field sensor. Despite these intriguing properties and application, only one high pressure study on structural transitions of Ag2Te up to 4 GPa has been reported while the new structures remain unsolved. Moreover, the LMR is found to be tunable by applying pressure merely to 1.7 GPa, highlighting pressure&’s role in tuning the band gap.
We performed in-situ synchrotron X-ray diffraction experiments up to 42.6 GPa at room temperature on Ag2Te powder. Three structure transitions are identified. Phase II is confirmed to exists in a narrow region between 2.2 GPa and 2.5 GPa, phase II transforms to phase III at 3.2 GPa, and phase IV occurs at 12.8 GPa and persists to the highest pressure. Phase III is solved to be an orthorhombic structure with space group Aba2 from both experiment and calculation. Calculated phase III&’s band structure shows the metallic nature.
5:00 AM - DDD2.09
Evidence for Polaron-ion Correlations in LixFePO4 from Nuclear Resonant Scattering
Sally June Tracy 1 Lisa Mauger 1 Jorge Munoz 1 Brent Fultz 1
1California Institute of Technology Pasadena USAShow Abstract
LiFePO4 is an important new material for electrodes of rechargeable Li-ion batteries. It offers low cost, low toxicity, thermal stability and high energy density. The conductivity mechanism in LiFePO4 is small polaron hopping. There is a keen interest in understanding the transport of Li ions and electrons within the lattice and improving the intrinsic electrical conductivity in LixFePO4. Valence fluctuations of Fe2+ and Fe3+ were studied in a solid solution of LixFePO4 by nuclear resonant forward scattering of synchrotron x-rays at elevated temperatures in a diamond-anvil pressure cell. The spectra acquired at different temperatures and pressures were analyzed for the frequencies of valence changes using the Blume-Tjon model of a system with a fluctuating Hamiltonian. The polaron hopping frequencies were analyzed to obtain activation energies and activation volumes. There was a large suppression of hopping frequency with pressure, giving an activation volume for polaron hopping that was large and positive, 5.8±0.7Å3. This large value indicates correlated motions of Li+ ions and polarons. It is plausible that the activation volume for polaron hopping is effectively enhanced by the electron-ion binding energy. Electrical conductivity requires decoupling of the ion and polaron motions, so their correlated motion may also suppress electrical conductivity in LiFePO4.
5:15 AM - *DDD2.10
Polymerization of sp-valent Materials at High Pressure
Stanimir Bonev 1 2
1Dalhousie University Halifax Canada2Lawrence Livermore National Laboratory Livermore USAShow Abstract
In this talk, I will review recent theoretical studies of sp-valent materials where transitions from molecular to covalent-bonded compounds are predicted. There has been a lot of interest in such systems for their potential application as novel energetic materials. One of the main obstacles for their discovery and characterization originates from the fact that they are usually only accessible at high pressure and temperature. Accordingly, our studies have focused on phase transitions of compressed systems at elevated temperatures. Predictions for several new phases will be presented and efficient methods for examining their stability will be discussed. I will also touch briefly on the role of (semi-) core electrons for the emerging material properties at extreme compression.
DDD1: New Synthesis Routes and Chemical Reactions
Tuesday AM, April 02, 2013
Marriott Marquis, Yerba Buena Level, Nob Hill AB
9:45 AM - *DDD1.01
Mixed Atomic and Molecular Phase of Dense Hydrogen and Deuterium
Eugene Gregoryanz 1 R. T. Howie 1 C. L. Guillaume 1 T. Scheler 1 A. F. Goncharov 2
1University of Edinburgh Edinburgh United Kingdom2Geophysical Laboratory, CIW Washington USAShow Abstract
We have used Raman and visible transmission spectroscopy to investigate dense hydrogen (deuterium) up to 310 (275) GPa at 300K, conditions previously inaccessible in a diamond anvil cell.1 At 220 GPa, a new phase of hydrogen (deuterium) has been discovered, characterized by emergence of intense, well defined low frequency Raman bands, together with the unprecedented softening of the vibron, nu;1, and appearance of a secondary vibron, nu;2. Analysis of the Raman spectra suggests a peculiar graphene-like structure consisting of both atomic and molecular layers2.
Through a series of low temperature experiments at high pressures, we observed deuterium (hydrogen) III-IV transformation, imposing constraints on the P-T phase diagrams.
The changes in optical spectra above 275 GPa suggest the presence of a new solid modification of H2(D2) closely structurally related to phase IV. No differences between hydrogen and deuterium were observed in absorption spectroscopic studies resulting in identical values for the band gap. The extrapolation of the band gap with pressure suggests its closure above 375 GPa for both isotopes.
 R.T. Howie, C.L Guillaume, T. Scheler, A.F. Goncharov and E. Gregoryanz, Phys. Rev. Lett., 108,125501 (2012)
 C. Pickard and Needs, Nature Physics, 3, 473 (2007)
10:15 AM - DDD1.02
Synthesis of BN and B-C-N Crystals under High Pressure
Takashi Taniguchi 1
1National Institute for Materials Science Tsukuba JapanShow Abstract
Hexagonal BN (hBN) and cubic BN (cBN) are known as the representative crystal structures of BN. The former is chemically and thermally stable, and has been widely used as an electrical insulator and heat-resistant materials. The latter, which is a high-density phase, is an ultra-hard material second only to diamond. Recently, some progresses in the synthesis of high purity BN crystals were achieved by using Ba-BN as a solvent material at high pressure crystal growth. Band-edge natures (cBN Eg=6.2eV and hBN Eg=6eV) were characterized by their optical properties. The key issue to obtain high purity crystals is to reduce oxygen and carbon contamination in the growth circumstances. It should be emphasized that hBN exhibits attractive potential for deep ultraviolet (DUV) light emitter [2,3 ] and also superior properties as substrate of graphene devices .
The purpose of this study is to understand the effect of carbon impurity in BN. Two approaches were conducted; (1) minimize the carbon impurity in hBN to realize its intrinsic nature, (2) realize the effect of the enrichment of carbon content in hBN. The study of carbon incorporation in hBN should be important not only for hBN&’s quality control but also for the interest of the fabrication of B-C-N ternary compounds as a new functional material. The function of well crystalline B-C-N compounds has not been realized so far.
Three types of experimental approaches were carried out; (1) synthesis of high purity hBN single crystals and its characterization with respect to residual carbon, (2) high temperature solid state diffusion of carbon into hBN and its characterization, and (3) high temperature annealing of turbostratic B-C-N(t-BCN) compound under high pressure. t-BCN flakes obtained by CVD process  was annealed near 3000C and 2GPa so as to become well crystallized.
At annealing near 3000C at 2GPa with graphite, carbon incorporation of 1E21/cm3 in hBN was achieved with exhibiting totally different CL spectra feature with high purity hBN crystals. Since major carbon contribution may affect the crystal structure of the 2-D layers stacking in hBN system, phase stability of BCN ternary phase will be introduced by the experimental results of high temperature annealing.
 T.Taniguchi, K.Watanabe, J.Cryst.Growth 303,525 (2007).
 K.Watanabe, T.Taniguchi and H.Kanda, Nature Materials, 3,404 (2004).
 K.Watanabe,T.Taniguchi,A.Niiyama,K.Miya, M.Taniguchi, Nature Photonics 3,591(2009).
 C.R.Dean, A.F.Young, K.Watanabe, T.Taniguchi, P.Kim, et.al.,Nat.Nanotech,5, 722(2010).
obtained by the same way after T.Sasaki, M.Akaishi,S.Yamaoka, Y.Fujiki and T.Oikawa, Chem.Mater, 5,695 (1993).
10:30 AM - DDD1.03
Optical Characterization of Shock-induced Chemistry in the Explosive Nitromethane Using DFT and Time-dependent DFT
Lenson Pellouchoud 1 Evan Reed 1
1Stanford University Stanford USAShow Abstract
A thorough understanding of chemistry in extreme environments is a major challenge in experimental as well as theoretical work. With continual improvements in ultrafast optical measurements and new methods for simulating chemistry on picosecond timescales, the opportunity is beginning to exist to connect experiments with simulations on the same timescale. In the present work, we compute the optical properties of the high explosive liquid nitromethane (CH3NO2) during the first 100 picoseconds of simulated detonation. We employ a perturbative Kubo-Greenwood formula with DFT electronic states, and then compare the results with optical spectra from time-dependent density functional theory (TDDFT), which typically yields more accurate spectra for molecular systems. At optical wavelengths, the TDDFT method offers a correction of up to 25% in the real part of conductivity relative to the Kubo-Greenwood calculation. We also study the effects of thermal electronic excitations on the calculated spectra, and find no discernible change at optical wavelengths. At low frequencies (<1eV), however, we find that obtaining accurate statistical sampling is problematic unless thermal excitations are included. With all methods, we observe a non-monotonic change in the entire spectrum of optical properties through the reaction zone as decomposition products evolve. We draw a connection between this evolution of optical properties and a variety of decomposition products, such as NO, CNO, CNOH, water, and others. These calculations offer some insight into interpretation of previous simulations, and some direction for ultrafast optical measurements on reactive materials.
11:15 AM - DDD1.04
Mechanism of the Shock-induced Wurtzite to Rock Salt Phase Transformation in Semiconductor Nanocrystals, Probed with Femtosecond X-Rays
Joshua Wittenberg 1 2 Timothy Miller 1 2 Erzsi Szilagyi 1 2 Katie Lutker 3 Florian Quirin 4 Klaus Sokolowski-Tinten 4 Paul Alivisatos 3 Aaron Lindenberg 1 2
1Stanford University Stanford USA2SLAC National Accelerator Laboratory Menlo Park USA3University of California, Berkeley Berkeley USA4Universitamp;#228;t Duisburg-Essen Duisberg-Essen GermanyShow Abstract
We have utilized laser-generated shock waves to induce the wurtzite to rock salt structural phase transformation in cadmium sulfide nanorods, and have probed the resulting dynamics using femtosecond X-rays at the Linac Coherent Light Source (LCLS).
Colloidally grown nanocrystals are the ideal model system with which to study phase transformations, because they are defect-free single crystalline domains. Though an ensemble of independent domains conveniently exhibits first-order kinetics, previous hydrostatic compression experiments have been limited to the second or millisecond timescale. Shock waves can compress a material on a timescale similar to that for a shear wave to traverse the sample, allowing experiments that can observe the transformation as it occurs, on a picosecond timescale. They can also compress materials in a uniaxial and inelastic fashion, accessing regions of the phase diagram not accessible under hydrostatic elastic compression. Simulations of this transformation have suggested a two-stage model consisting of a compression along the c-axis to form a 5-coordinate h-MgO intermediate followed by compressive shear along the a-axis, with the transformation rate limited by the shear step. A direct structural probe of the mechanistic pathway has not been available experimentally, however, due to the limited time-resolution and/or photon flux of existing X-ray sources.
By coupling shock wave compression of nanocrystalline samples with an ultrashort-pulsed X-ray diffraction probe provided by the new LCLS, we have been able to collect the first snapshots of this transformation in real time, in a sample comprised of non-interacting crystalline domains.
We have observed a stress-dependent transition path. At higher peak stresses, the majority of the sample is converted directly into the rock salt phase, with no evidence of an h-MgO intermediate prior to rock salt formation. At lower peak stresses, an h-MgO structure is observed. Additionally, the observed transformation stress is ~3GPa, significantly below the ~7GPa required under hydrostatic compression, confirming previous observations of shear-catalyzed structural transformation under shock compression.
11:30 AM - DDD1.05
Synthesis, Characterization of Elastic and Electrical Properties of Dense BCx Nano-phases Synthesized under High-pressure and High-temperature
Pavel Zinin 1 Li Chung Ming 1 Tayro Acosta 1 Ruth Jia 1 Hope Ishii 2 Eric Hellebrand 1 Ivan Trojan 3
1University of Hawaii Honolulu USA2Lawrence Livermore National Laboratory Livermore USA3Max-Planck-Institut famp;#252;r Chemie Mainz GermanyShow Abstract
A direct transformation of graphitic phases from BCx system with high concentration of boron (x>1.5) under high pressure and high temperature was studied. It was found that graphitic phases transform to new cubic BCx (c-BC3, c-B2C3) phasesin a diamond anvil cell (DAC) at high temperature, 2200 K, and high pressure, 31 GPa. The atomic structure, bonding between atoms, and nanostructure was determined using transmission electron microscopy (TEM), x-ray diffraction and transmission electron microscopy-electron energy loss spectroscopy (EELS). The electrical properties of the BC2 and B2C3 graphitic phases were measured. The electrical resistivity of BC2 and B2C3 phases appeared to be slightly higher than that of amorphous carbon and 1016 times smaller than that of diamond. Elastic properties of the BCx phases were determined from Brillouin scattering measurements
12:00 PM - DDD1.07
Inducing Extreme Pressures in Si by fs-laser Confined Micro-explosion
Ludovic Rapp 2 Bianca Haberl 1 Jodie Bradby 1 Eugene Gamaly 2 Jim Williams 1 Saulius Juodkazis 3 Andrei Rode 2
1The Australian National University Canberra Australia2The Australian National University Canberra Australia3Swinburne University of Technology Hawthorn AustraliaShow Abstract
Ultra-fast laser-induced micro-explosion in confined geometries is a method for simultaneously creating Tera Pascal (TPa) pressures and temperatures above 105 K in table-top experiments.[1,2] This method allows ultra-high heating ~1017 K/s and quenching ~1014 K/s rates to be achieved, while keeping the transformed material confined inside the pristine crystal. As a result, the new exotic states of matter that arise have their genesis in plasma, in stark contrast to compressing the solid state as, for example, in conventional diamond anvil cells. In this work we exploit the geometry of a semiconductor/oxide structure to enable the highly localized formation of ultra-high-pressure to go beyond the GPa regime by promoting the formation of Warm Dense Matter (WDM).
The conditions of confinement were realized by focusing fs-pulses on a Si surface buried under a 10-mu;m thick SiO2-layer formed by oxidation. 170-fs laser pulses with the energy up to 2.5 mu;J were tightly focused to the intensity well above the threshold ~1012 W/cm2 for optical breakdown and plasma formation. Samples of the shock-wave modified regions were analysed using focused-ion beam milling, scanning and transmission electron microscopy and Raman microspectroscopy.
TEM analysis of the laser-modified zone showed that a void was formed surrounded by a shock-wave-modified Si. The material surrounding the void was found to contain a number of different phases including amorphous Si and several new silicon polymorphs with inter-atomic spacing that cannot be attributed to any known polymorph of silicon. Indeed, electron dark-field imaging clearly shows that several phases form fully within the silicon matrix. At least twelve polymorphs of Si with different electronic and optical properties are known to exist at pressures up to 250 GPa. In our samples the new silicon phases coexist with the known structures of hexagonal-diamond (Si-IV), tetragonal (Si-VIII) and rhombohedral (Si-XII) phases, as well as diamond-cubic silicon crystal Si-I. The formation of these polymorphs shows that Si has undergone pressure-induced transitions into the realm of the metallic high-pressure phases that are conventionally formed above 11 GPa.
The phases created by micro-explosion are important from the fundamental point of view of giving further insights into the high-pressure behaviour of silicon. The results further demonstrate that confined micro-explosion opens up new possibilities for studies of WDM at the laboratory tabletop, and opens up new routes for formation of super-dense and super-hard materials.
 A. Vailionis, E. G. Gamaly, V. Mizeikis, W. Yang, A. Rode, S. Juodkazis, Nature Communications 2, 445 (2011).
 E. G. Gamaly, A. Vailionis, V. Mizeikis, W. Yang, A. V. Rode, S. Juodkazis, High Energy Density Physics, 8, 13-17 (2012).
12:15 PM - DDD1.08
The Importance of Quantum Nuclear Effects in Shocked Methane
Tingting Qi 1 Evan Reed 1
1Stanford University Stanford USAShow Abstract
We find that quantum nuclear effects result in the onset of methane dissociation at 40% lower pressure on the shock Hugoniot than observed with classical molecular dynamics. The temperature shift associated with quantum heat capacity is determined to be the primary factor in this shift. Classical molecular dynamics simulations are only approximately correct for temperatures that are higher than the Debye temperature. The lack of quantum corrections may cause errors of magnitudes comparable or greater than those due to poor representation of the potential energy surface. We have developed a new methodology for atomistic simulations of shock-compressed materials that, for the first time, incorporates semi-classical quantum nuclear effects self-consistently. A modification of the Multi-Scale Shock Technique (MSST) is introduced so that the system couples to a quantum thermal bath described by a colored noise Langevin thermostat. The new method, QB-MSST, is of comparable computational cost to MSST and self-consistently incorporates quantum heat capacities and Bose-Einstein Harmonic vibrational distributions. As a first test, we study shock-compressed methane using the ReaxFF potential. The Hugoniot curves predicted from the new method are found comparable with existing experimental data.
12:30 PM - *DDD1.09
Simulation of Molecular Mixtures at Extreme Conditions
Sandro Scandolo 1
1The Abdus Salam International Centre for Theoretical Physics Trieste ItalyShow Abstract
Mixtures of simple molecules, primarily methane and water, are the main components of the interiors of the giant planets Neptune and Uranus. Simulations and experiments on the individual components at the conditions present in the middle layers of such planets show that methane disproportionates into carbon-rich species and water dissociates to form an ionic fluid which becomes electronically conducting at the conditions of the deepest layers of the planets. More recent simulations on water/methane mixtures suggest a pressure-induced softening of the methane-water
intermolecular repulsion that points to an enhancement of mixing under extreme conditions. Ionized water causes the progressive ionization of methane and the mixture becomes electronically conductive at milder conditions than pure water. Calculations on the crystalline counterparts, methane hydrate clathrates, suggest however a different picture: mixtures at low temperature become increasingly unstable, with increasing pressure, towards phase separation, despite the prediction of a solid-solid phase transition between MH-III, the known high-pressure form of methane hydrate, and a new hypothetical phase. (*) Work done in collaboration with M.-S. Lee, N. Pantha, N. Adhikari.
Brent Fultz, California Institute of Technology
Giulia Galli, University of California Davis
Malcolm Guthrie, Carnegie Institution of Washington
Chi-Chang Kao, Stanford Synchrotron Radiation Lightsource
Symposium Support Efree, a DOE-funded Energy Frontier Center
DDD4: Experimental and Computational Techniques
Wednesday PM, April 03, 2013
Marriott Marquis, Yerba Buena Level, Nob Hill AB
2:30 AM - *DDD4.01
High-pressure Synthesis of New Energy Related Materials via Formation of New Bonding Patterns
Alexander Goncharov 1
1Carnegie Institution of Washington Washington USAShow Abstract
The search for new materials synthesized under extreme conditions of high pressure and high pressure is currently actively pursued. There are multiple theoretical predictions for superior material properties, which can be achieved [1-3]. These include ultra-hardness, superior transport properties such as electrical and thermal conductivity, high energy-density, high-temperature superconductivity, ability to storage hydrogen, etc. In the majority of cases, synthesis of new materials at high pressures is based on changes in the equilibrium chemical bonding . Recent experiments documented such changes in a number of systems that include simple molecules (polymerization and ionization) and simple metals (electronic localization). Also a number of new heterogeneous compounds have been reported by forming chemical bonding, which is unstable at ambient conditions. Implications of this novel extreme chemistry for synthesis of new materials for practical applications remain challenging because high-pressure bonding patterns are often thermodynamically unstable at ambient pressure . Search for a recovery mechanisms or attempts of synthesis in nominally metastable conditions require extensive collaborative efforts of experiment and theory. Here, I emphasize the importance for this task of in situ fast diagnostic methods such as x-ray diffraction and optical spectroscopy. I will also present at the meeting new results on synthesis of materials containing hydrogen, nitrogen, xenon, and halogens.
This work has been performed in collaboration with M. Somayazulu, V. V. Struzhkin, V. Prakapenka, E. Stavrou, A. Oganov, Z. Konopkova, H.-P. Liermann. I acknowledge the support of NSF, EFRee (DOE), DARPA, Army Research Office, Deep Carbon Observatory, and Carnegie Institution of Washington.
 N. W. Ashcroft, Phys Rev Lett 21, 1748 (1968).
 C. Mailhiot, L. H. Yang, and A. K. McMahan, Phys. Rev. B 46, 14 419 (1992).
 A. Y. Liu and M. L. Cohen, Science, 245, 841 (1989).
 P. F. McMillan, Nature Materials 1, 19 (2002).
 V. V. Brazhkin, A. G. Lyapin AG., Nat Mater. 3, 497 (2004).
3:00 AM - *DDD4.02
Synchrotron X-Ray and On-line Optical Techniques for High Pressure Research
Vitali Prakapenka 1
1University of Chicago Argonne USAShow Abstract
Over the past two decades, high pressure research has made breakthrough progress in many fields of science mainly due to significant advances in development of both high pressure vessels (diamond anvil cell and large volume press) and high brilliance synchrotron based techniques, including high resolution x-ray micro-diffraction, x-ray spectroscopy (absorption, emission, resonance), micro-imaging, inelastic and nuclear resonance scattering. Combination of double-sided laser heating with synchrotron x-ray radiation has stimulated synthesis and investigation of new materials with unique composition and properties in-situ at high temperatures and high pressures in the diamond anvil cell. Equation of state, structure, phase transformations, element partitioning, electronic and optical properties of various materials (single crystal, powder, nano-crystalline, amorphous solid and fluids) have been successfully studied at extreme conditions with help of the lasers and x-ray beams. Recent developments in pulse laser heating technique, including application of fiber lasers and flat top laser beam shaping optics, result in significant improvement in synthesis of new metastable materials with tuneable composition and properties controlled in-situ with high resolution x-ray and optical techniques in time-domain mode. The details and application of the synchrotron and optical techniques for studies unique physical and chemical properties of materials in-situ at extreme conditions will be discussed on example of iron-carbon system, self-assembled PbS supercrystals, Si nanocrystals etc.
3:30 AM - DDD4.03
A Suite of Multiscale Synchrotron Techniques for High Pressure Research
Wenge Yang 1
1Carnegie Institution of Washington Argonne USAShow Abstract
Over last decades, both synchrotron radiation techniques and high pressure research have made great progress. Advanced synchrotron capabilities with high spatial resolution, high flux, high energy resolution and high coherence provides us many new avenues to conduct advanced high pressure researches. In this talk, we will mainly focus on the new developments of the nanoscale imaging and diffraction studies on the internal strain distribution, valence transition, and chemical composition under high pressure. Recently progress on coherent diffraction imaging, differential aperture 3d x-ray diffraction microscopy, absorption correlation and XANES type tomography will be presented and outlook will be discussed.
4:15 AM - DDD4.04
Formation of Iron Melt Channels in Silicate Perovskite at Earthrsquo;s Lower Mantle Conditions
Yingxia Shi 1 Wendy Mao 1 2 Yijin Liu 2 Li Zhang 4 Wenge Yang 3
1Stanford University Stanford USA2SLAC National Accelerator Laboratory Stanford USA3Carnegie Institution of Washington Argonne USA4Carnegie Institution of Washington Washington USAShow Abstract
Core-formation represents the most significant differentiation event in Earth&’s history, but we still lack very basic information about this early portion of our planet&’s history. Many previous experimental results have ruled out percolation as a major core formation mechanism for Earth at upper mantle conditions, but until now experimental results at lower mantle conditions were not possible due to the ultrahigh pressure-temperatures which lead to very small sample sizes requiring nanoscale resolution. We investigated the ability of a liquid iron alloy to form an interconnected melt network with (Mg,Fe)SiO3 perovskite (pv) under Earth&’s lower mantle conditions by combing several cutting-edge techniques, including laser-heated diamond anvil cell at 16-IDB of the Advanced Photon Source (APS) with nanoscale synchrotron X-ray tomography. We imaged a dramatic change in the shape of the iron-rich melt in the three-dimensional (3D) reconstructions of samples prepared at varying pressures and temperatures, providing evidence that percolation would be an efficient mechanism at Earth&’s lower mantle conditions. This has significant implications for the evolution of the planet, Earth&’s early thermal history, and the large scale geochemical distribution of elements.
4:30 AM - DDD4.05
High-resolution Three-Dimensional Characterization of Advanced Ceramic Textile Composites under In situ Loading at 1750deg;C
Hrishikesh A Bale 1 2 Siyuan Xin 1 2 Abdel Haboub 3 David B. Marshall 4 Brian N Cox 4 Robert O. Ritchie 1 2
1University of California Berkeley USA2Lawrence Berkeley National Laboratory Berkeley USA3Lawrence Berkeley National Laboratory Berkeley USA4Teledyne Scientific LLC Thousand Oaks USAShow Abstract
Textile ceramic composites represent the enabling materials for several major ultrahigh-temperature structural applications, specifically advanced gas-turbine engines and for leading edges and contact surfaces for future hypersonic flight vehicles. Extreme service conditions of temperatures from 1200°C to potentially well above 1700°C in combination with service loads and hostile environmental atmospheres are well beyond the realm of current commercial structural materials. Using novel strategies in materials and coatings along with integral 3-D architectural design, woven ceramic-matrix composites (CMC&’s), such as SiC-SiC materials, make the development of such ultrahigh-temperature structures a feasible proposition. Lifetime prediction and damage assessment for such complex architectures presents a formidable challenge though, as the collection of reliable physical and engineering mechanical data, not to mention the characterization of damage in 3-D, at temperatures above 1200°C, is so difficult. To this end, we have developed a facility to perform such characterization using synchrotron x-ray micro-tomography capable of subjecting samples to tensile loads at temperatures of 2300°C, which has proven to be a tool of choice for non-destructively evaluating the component in three-dimensions at spatial resolutions around a micron. We report several phenomena governing failure that occur over time in a model SiC/SiC fiber-matrix composite above 1700°C ranging from cracking within individual fibers to the fracture of entire fiber bundles/tows at these extreme temperature conditions system. This new ability to image complex 3D materials undergoing failure under combined extreme physical conditions, for the first time opens new possibilities for evaluating ceramic textile materials in real time. Indeed, the technique can be extended in studying not just textile composites but a myriad of new structural materials.
4:45 AM - *DDD4.06
Multianvil High-pressure Technology and Synthesis of Novel Polycrystalline Materials
Tetsuo Irifune 1
1Ehime University Matsuyama JapanShow Abstract
Kawai-type multianvil apparatus (KMA or MA6-8 apparatus) yields quasi-hydrostatic pressures of up to 30 GPa and temperatures to 3500K in relatively large volumes of 10-1 - 104 mm3 compared to those available in diamond anvil cell (typically <10-3 mm3), depending on the pressure range and capacity of the press. We succeeded to synthesize well-sintered bodies of nano-polycrystalline diamond (NPD) by direct conversion of graphite at pressures greater than ~12 GPa and temperatures between 2300 and 3000K using KMA, which was found to possess unique characteristics of nano-textures, ultra-hardness, high toughness, high thermal resistance, high optical transparency, etc. NPD rods even as large as 1 cm in both diameter and length have been successfully produced in a large-volume KMA (BOTCHAN-6000), recently constructed at the Geodynamics Research Center of Ehime University. Syntheses of other consolidated nano- to micro-polycrystalline high-pressure phases, such as nano-polycrystalline stishovite (NPS) and micro-polycrystalline garnet (MPG), have also been made using similar techniques. In this talk, recent progresses in multianvil technology for materials synthesis and its application to synthesis of the novel polycrystalline high-pressure phases are reviewed with some future perspectives.
5:15 AM - *DDD4.07
Crystal Structure Prediction and Computational Materials Design: New Breakthroughs
Artem R. Oganov 1 Andriy O. Lyakhov 1 Qiang Zhu 1
1SUNY Stony Brook Stony Brook USAShow Abstract
The evolutionary methodology USPEX for crystal structure prediction  reliably stable and low-energy metastable structures of a given compound at given P-T-conditions . Theory of energy landscapes  gives tools that greatly enhance structure prediction. We generalized USPEX to variable-composition systems (in which case it finds not only the crystal structures, but also chemical compositions of all stable compounds in a multicomponent system ) and to molecular crystals (to efficiently find optimal packing of molecules). Evolutionary metadynamics  is another powerful approach to find both the ground state and metastable structures kinetically accessible from the initial structure. USPEX can be used also to find structures and compositions possessing optimal physical properties [6,7], which is invaluable for computational materials design.
The following results will be discussed:
1. High-pressure behavior of hydrocarbons: new high-pressure structures of methane  and its phase diagram , and studies of graphane .
2. Prediction of Fe2C (not FeC3 or Fe7C3, as believed up to now) as the stable carbide at conditions of the Earth&’s inner core .
3. For the old puzzle of a new allotrope of carbon, produced by room-temperature compression of graphite, transition path sampling calculations (also enabled in USPEX package - http://han.ess.sunysb.edu/~USPEX), we have established the monoclinic (C2/m) structure of M-carbon as kinetically likeliest phase .
4. Prediction of densest possible structures of carbon , with interesting optical and electronic properties. Search for the hardest phase of carbon  showed that no phase of carbon can be harder than diamond.
5. Prediction of thermodynamically stable oxides of xenon at high pressure .
6. Demonstration  that the claimed ultrahardness of TiO2-cotunnite is an experimental artifact and no phase of TiO2 can have hardness above 16 GPa, i.e. all possible phases of TiO2 are much softer than even common corundum. Thus, it is clear that contrary to previous claims TiO2 cannot be considered as the hardest known oxide.
1. Oganov A.R., Glass C.W., J.Chem. Phys. 124, 244704 (2006).
2. Oganov A.R., Lyakhov A.O., Valle M. Acc. Chem. Res. 44, 227-237 (2011).
3. Oganov A.R., Valle M., J.Chem.Phys. 130, 104504 (2009).
4. Zhu Q., et al. Acta Cryst. B, in press. (2012).
5. Zhu Q., Oganov A.R., Lyakhov A.O. Cryst.Eng.Comm., in press. (2012).
6. Lyakhov A.O., Oganov A.R. Phys. Rev. B84, 092103 (2011).
7. Zhu Q., et al. Phys. Rev. B83, 193410 (2011).
8. Gao G., Oganov A.R., et al., J.Chem.Phys. 133, 144508 (2010).
9. Wen X.D., et al. Proc. Natl. Acad. Sci. 108, 6833-6837 (2011).
10. Bazhanova Z.G., Oganov A.R., Gianola O. Uspekhi Physics 55, 489-497 (2012).
11. Boulfelfel S.E., Oganov A.R., Leoni S. Scientific Reports 2, 471 (2012).
12. Zhu Q., et al. (2012). Nature Chemistry, in press (2012).
5:45 AM - DDD4.08
Micro Neutron-diffraction at the Spallation Neutron Source
Malcolm Guthrie 1 Reinhard Boehler 1 Jamie Molaison 2 Antonio dos Santos 2 Christopher Tulk 2 Kuo Li 1
1Carnegie Institution of Washington Washington USA2Oak Ridge National Laboratory Oak Ridge USAShow Abstract
The intrinsically limited flux available from conventional neutron sources has typically constrained sample volumes to be many orders of magnitude larger than their synchrotron counterparts. This leads to considerable limitations where available sample volumes are highly constrained, or where extreme sample environments demand the smallest possible samples. As a consequence, the many benefits of neutron techniques (for example light atom sensitivity, high spatial resolution and the ability to measure long-range magnetic order) have been unavailable for many important systems.
In the past, high-pressure science has been a strong driver towards minimizing sample size and, by the mid-1990s&’, it was possible to conduct good quality neutron-diffraction measurements from volumes as small as ~30mm3 . Our own developments, aimed at maximizing sample pressures, have greatly reduced the required volumes for neutron diffraction. Using the intense beams of the Spallation Neutron Source at Oak Ridge National Laboratory and with an optimized diamond-anvil cell, developed at the Carnegie Institution, we have measured refinable quality neutron-diffraction data from samples as small as 0.05mm3. This capability is not only a breakthrough for high pressure, where we have doubled the available pressure range to 60 GPa, but may also have broad applicability for other fields where neutron characterization of micro-samples is important.
 S. Klotz et al Applied Physics Letter 66 1735 (1995).
DDD5: Poster Session
Wednesday PM, April 03, 2013
Marriott Marquis, Yerba Buena Level, Salons 7-8-9
9:00 AM - DDD5.01
CO2 Capture by Modified Kaolinite Minerals
De Long Lu 1 Yen-Hua Chen 1
1National Cheng Kung University Tainan TaiwanShow Abstract
After industrial revolution, the CO2 emission to the atmosphere has gradually increased, therefore it is more important to reduce the CO2 discharge. Kaolinite, a common caly mineral, is a dioctahedral 1:1 phllosilicate formed by Si-O tetrahedral sheets and Al-O octahedral sheets. In this study, kaolinite minerals are used to capture CO2 due to their layer structures and high adsorption efficiency. Moreover, the surface area and porosity of kaolinites are enhanced by acidic treatment. Kaolinites are also modified with MEA and EDA to promote the ability of CO2 adsorption. The crystalline structures before and after acidic treatment and amine-modification would be analyzed by using X-ray diffractometer. The specific surface area and porosity would be examined by BET analyzer. The morphology would be observed by scanning electron microscope.
The results show that the best acid-treatment condition for kaolinite is with 3M H2SO4, reaction time of 10 hr, stirring rate of 100 r.p.m at 95 degrees . The specific surface area increase from 18 m2/g of the original kaolinite to 83 m2/g of acid-treated kaolinite. And then the acid-treated kaolinite was modified by MEA and EDA. The CO2 adsorption capacity was examined by thermo-gravimetric analyzer. It is observed that kaolinite with amine-modification has a better CO2 adsorption capacity than that only with acid-treated kaolinite. The CO2 adsorption mechanism via the property analysis before and after CO2 adsorption will be discussed latter.
9:00 AM - DDD5.02
Phase Transformations in Silicon Induced by Both Diamond Anvil and Indentation at Elevated Temperatures
Jim Williams 1 Kiran Mangalampalli 1 Malcolm Guthrie 2 Bianca Haberl 1 Jodie Bradby 1
1The Australian National University Canberra Australia2Carnegie Institution of Washington Washington DC USAShow Abstract
It is well known that pressure-induced phase transformations can occur in silicon both by indentation and in a diamond anvil cell.[1,2] In both cases, diamond cubic (dc) silicon undergoes a transformation to a metallic β-Sn phase (so called Si-II) at 11.3 GPa but on unloading the behaviours are significantly different. Under diamond anvil experiments Si-II first transforms to the semiconducting r8 phase (Si-XII) at a pressure of 9 GPa and Si-XII further transforms to the semi-metal bc8 (Si-III) phase at ~2 GPa. However, during indentation the unloading behaviour is decidedly different with Si-II transforming directly to amorphous silicon under fast unloading and to a mixture of the crystalline Si-XII and Si-III phases on slow unloading.
In this work we directly compare the Si phase transformation behaviour under the two pressure-induced transformation methods as a function of temperature in an attempt to unravel the different transformation behaviours. In the diamond anvil case we find that Si-XII transforms at 10 GPa to dc Si at a temperature of 250°C whereas at 3 GPa Si-III transforms to hexagonal silicon (Si-IV) at around 140°C. Under indentation, the determination of the phases present is more difficult. However, at room temperature and pressure a mixture of Si-XII/Si-III phases transforms typically to an as yet unidentified Si-XIII phase at 150°C and further to dc-Si at about 250°C. However, when the indentation is performed at temperatures up to 200°C, the transformation behaviour is even more complex. In these cases, we have examined the end phases by both TEM and Raman spectroscopy as well as the nature of the unloading curves. In some cases, notable for 200°C, the end phase after unloading is dc-Si, whereas at temperatures up to 150°C there is clear evidence for Si-XII/Si-III end phases. Furthermore, under fast unloading for temperatures of 100-150°C, there is a high probability of formation of crystalline Si-XII/Si-III phases, in contrast to a 100% probability of forming an amorphous silicon end phase under the same unloading conditions at room temperature. We offer possible explanations for this complex phase transformation behaviour in terms of the thermodynamics, transformation kinetics and nucleation barriers for the specific phases.
1. J. Crain, G. J. Ackland, J. R. Maclean, R. O. Piltz, P. D. Hatton, and G. S. Pawley, Phys. Rev. B 50, 13043 (1994).
2. J. E. Bradby, J. S. Williams, J. Wong-Leung, M. V. Swain, and P. Munroe, J. Mater. Res. 16, 1500 (2001).
9:00 AM - DDD5.03
Diamondoids under High Pressure
Fan Yang 1 Yu Lin 1 Wendy Mao 1 2
1Stanford Univerity Stanford USA2SLAC National Accelerator Laboratory Menlo Park USAShow Abstract
Diamondoid molecules are ultra stable, saturated hydrocarbons consisting of fused carbon cages superimposing on the diamond lattice, originally found in petroleum. These hydrocarbons, especially the higher diamondoids, have been of great interest in recent years due to their potential role in nanotechnology, electronics, and medical applications. However, the large number of possible intermediates, reaction pathways, and complex reaction kinetics make the synthesis of higher diamondoids extremely difficult.
We investigated the effect of pressure on  tetramantane structural stability and phase transition by combing angel-dispersive synchrotron X-ray powder diffraction (XRD) and in situ high pressure Raman spectroscopy in diamond anvil cells up to 20GPa. XRD shows that  tetramantane displays a molecular orientation related phase transition from a monoclinic P21/n structure to triclinic P1 structure occurs at around 13GPa and the transition was almost complete at around 20GPa. In addition, the high pressure phase shows a large metastability field upon decompression. Raman studies also confirmed this phase transition and the metastability of the high pressure phase based on the peak splitting and pressure shifts, as well as changes in the relative intensity of the most intense peaks. JADE and GSAS were applied to index the diffraction pattern and refine the unit cell parameters. We also applied 3rd order Birch-Murnagahan equation of state to fit the P-V curve. Our study may have implications for developing alternative approaches to synthesize higher diamondoids from the lower ones.
9:00 AM - DDD5.05
High Pressure Raman Studies on Orthochromites GdCrO3 and EuCrO3 up to 25 GPa
Venkata Srinu Bhadram 1 Chandrabhas Narayana 1
1Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) Bangalore IndiaShow Abstract
Rare-earth orthochromites (RCrO3) have interesting magnetic structure with two magnetic ordering temperatures related to magnetic R3+ and Cr3+ ions. Recent studies [2,3] suggests that these materials are multiferroic when R3+ has non-zero magnetic moment (as in Gd3+, Sm3+, Tm3+ etc.) which is interesting for both theoretical as well as experimental community as these materials are novel and the mechanism driving multiferroicity in these materials is unknown. Though pressure played a key role in understanding many ferroelectric oxides in the past,  very little is known about the effect of pressure on magnetoelectric multiferroics.
Our present high pressure Raman studies on GdCrO3 and EuCrO3 up to 25 GPa reveal that the behaviour of these systems under pressure is distinct compared to that of temperature. Our preliminary analysis shows two successive phase transitions at 1.7 and 15 GPa in the case of EuCrO3. Transition at 1.7 GPa is accompanied by discontinuities in phonon frequencies indicating a structural phase transition. At 15 GPa, we have seen frequency crossover of CrO6 octahedral rotational modes (B1g and Ag) indicating that these phonons are coupled. It is noteworthy to say that similar coupled phonons are observed in BaTiO3 across ferroelectric transition around 2 GPa. In case of GdCrO3 we have not seen any coupled phonons. However a splitting of degenerate CrO6 rotational modes (around 400 cm-1) is observed at 5 GPa indicating a possible structural phase transition. A comparative study of the pressure effects on the structural parameters of these materials as well as other RCrO3 (R= Lu, Eu, Sm) is under way which would give more insights into the phase transitions discussed above.
 T. Yamaguchi, and K. Tsushima, Phys. Rev. B 8, 5187 (1973).
 B. Rajeswaran, D. I. Khomskii, A. Sundaresan, and C. N. R. Rao, arXiv: 1201.0826v1 [cond-mat.mtrl-sci](2012).
 V. S. Bhadram, B. Rajeswaran, A. Sumdaresan, C. Narayana, arXiv:1205.3551v1 [cond-mat.mtrl-sci](2012).
 G. Kh. Rozenberg, and M. P. Pasternak, Phase. Trans. 80, 1131 (2007).
 A. K. Sood, N. Chandrabhas, D. V. S. Muthu, A. Jayaraman Phys. Rev. B 51, 8892 (1995).
9:00 AM - DDD5.06
Cryogenic Thermal Expansion Behavior and Impact Resistance of PPO/PA Blends Reinforced with Pitch Carbon Fibers
Jin Woo Yi 1 Hee Jeong Won 2 Byung Mun Jung 1 Wonoh Lee 1 Sang Bok Lee 1 Moon Kwang Um 1
1Korea Institute of Materials Science Changwon Republic of Korea2University of Science amp; Technology (UST) Daejeon Republic of KoreaShow Abstract
Polymer blends have attracted considerable interests from industries due to one of developing strategies for new polymer materials as well as their balanced properties. A typical example of polymer blends is the polyphenylene oxide/polyamide (PPO/PA) and the blend has been applied to many fields, for instance, automotive parts, because it achieves a good combination of the processability and chemical resistance of PA with the high impact resistance and low coefficient of thermal expansion (CTE) of PPO. However, the blend suffers from some drawbacks when this is used as one of exterior parts of automotive for the weight reduction. First, PPO/PA blend still has relatively high CTE compared to steel, which results in a poor external appearance if they are nearby assembled. The other is that the addition of some inorganic fillers to lower CTE of the blend seriously weakens the impact strength. Therefore, new filler material to overcome the trade-off relationship between CTE and impact strength is highly necessary. In this study, we consider pitch-based short carbon fibers as a potential filler for PPO/PA blend because they display extremely good dimensional stability and moderate cost compared to PAN-based carbon fibers. We focus on the effect of chemical surface treatment on the impact strength, CTE and cryogenic CTE. This work may facilitate not only the expansion of the usage for automotive but also additional opportunities for cryogenic applications.
9:00 AM - DDD5.07
N-heterocyclic Carbene Chelated Metal Complexes as Polymerization Catalysts
Amer A El-Batta 1 Robert H Grubbs 2
1King Fahd University of Petroleum and Minerals Dhahran Saudi Arabia2California Institute of Technology Pasadena USAShow Abstract
N-Heterocyclic carbenes (NHCs) are a class of stable carbenes that have found increasing use as ligands for transition metal catalysts . A previous work from our group has established a convenient route for the synthesis of a novel class of chelating NHC and their ability to form complexes with late (nickle  and palladium ) and early metals (titanium and zirconium) . The Ti and Zr complexes were isolated as bis-ligated complexes that interestingly had trans arrangement of the NHC ligands. When combined with methylaluminoxane, these complexes were active for the homopolymerization of ethylene as well as the copolymerization of ethylene with 1-octene or norbornene. It has been observed that the polyethylene produced is linear high density polyethylene. The Ti complexes were also employed to produce highly syndiotactic polystyrene. Polystyrene is an important commodity plastic that exhibits many desirable characterisitics that make it useful in many automative, electrical, and consumer applications, and its properties are directly governed by its tacticity.
 M. Melaimi, M. Soleihavoup, G. Burtrand, Angew. Chem. Int. Ed. 49 (2010) 8810-8849.
 A. W. Waltman, T. Ritter, R. H. Grubbs, Organometallics 25 (2006) 4238-4239.
 A. W. Waltman, R. H. Grubbs, Organometallics 23 (2004) 3105-3107.
 A. El-Batta, A. W. Waltman, R. H. Grubbs, J. Organomet. Chem. 696 (2011) 2477-2481.
9:00 AM - DDD5.08
Structure of Sb2Te3 Metastable Phase
Nadezhda Serebryanaya 1 Ivan Kruglov 1 Nataliya Lvova 1 Vladimir Blank 1
1Technological Institute for Superhard and Novel Carbon Materials Troitsk Russian FederationShow Abstract
Earlier we manufactured the metastable phases Sb2Te3 (Sb2Te3 II) and Bi0,4Sb1,6Te3 using the method of quenching under high pressure after treatment at P = 4.0 GPa and T = 400 - 850 C (S. G. Buga, N. R. Serebryanaya, G. A. Dubitskiy, E. E. Semenova, V. V. Aksenenkov, V. D. Blank. “Structure and electrical properties of Sb2Te3 and Bi0,4Sb1,6Te3 metastable phases obtained by HPHT treatment”. High Pressure Research, Vol. 31, No. 1, March 2011, 86 - 90.). In the present work conditions of obtaining Sb2Te3 II were studied at different interval of pressure and temperatures. The powder X-ray diffraction patterns of this phase and wide-spread thermoelectric material Bi0,4Sb1,6Te3 are just the same and similar to the known monoclinic structure α - As2Te3. We propose the space group C2/m with less monoclinic distortion β ~ 92,250 0 than that of α -As2Te3, the preliminary calculated parameters of unit cell dimensions are a ~ 14,91 Å, b ~ 3,80 Å, c ~ 10,62 Å. Calculations were made by methods of full profile analysis. In the structure of Sb2Te3 II there are 14 unknown parameters (10 coordinates and 4 cell parameters), which are very difficult to fit to experimental XRD patterns. This is why we try to calculate them by methods of quantum chemistry. The energy of system, atomic bond orders, atomic orbitals&’ occupancy, molecular, localized orbitals were calculated. Results of geometry calculation correlate with data obtained from XRD analysis qualitatively. The refinement of structure will be continued by the methods of density functional theory (DFT). It was carried out theoretical study of relative stability of both Sb2Te3 phases (initial and metastable). Preliminary estimations showed that the energy of Sb2Te3 II per one atom is higher on 0,03 eV/atom than energy of equilibrium phase (Sb2Te3 I). After two years the process of reverse transformation from Sb2Te3 II to Sb2Te3 I has started, it proves the reliability of ours estimations. Earlier the electrical resistivity and the Hall coefficient were measured in the temperature range of T = 77 - 450 K. The negative Hall coefficient indicates the dominant electron type of carriers at temperatures up to 380K in metastable phase Sb2Te3 II. Above this temperature, the p - type conductivity proper to the initial phase, what confirms the reverse transformation. Annealing of Sb2Te3 II shows that the reverse transformation occurs at T = 400 C during two hours. Because the parameters of HPHT treatment are sufficiently low and at 200 C starts the appearance of the most intensive peaks of both Sb2Te3 II and Bi0,4Sb1,6Te3 II phase, we suppose that monoclinic phase could be generated in initial phase during the process of mechanical alloying. These metastable phases could affect on the thermoelectric properties (figure of merit ZT) of researched materials.
DDD3: Amorphous and Liquid Materials and Defects
Wednesday AM, April 03, 2013
Marriott Marquis, Yerba Buena Level, Nob Hill AB
9:30 AM - DDD3.01
Long-Range Topological Order in Metallic Glass
Qiaoshi Zeng 1 Hongwei Sheng 3 Yang Ding 2 Lin Wang 2 5 Jian-Zhong Jiang 4 Wendy Mao 1 6 Ho-Kwang Mao 7 2
1Stanford University Palo Alto USA2Carnegie Institution of Washington Argonne USA3George Mason University Fairfax USA4Zhejiang University Hangzhou China5Jilin University Changchun China6SLAC Menlo Park USA7Carnegie Institution of Washington Washington USAShow Abstract
Glass plays an essential role in science and industry. An accurate description of atomic structure could underpin our understanding of glass and helps to design better materials. Unfortunately, due to the loss of identifiable symmetry, the structure of glass is far less known compared to that of crystal. Although it has been established that nominally “disordered” glass structure may still have short-range order of the nearest-neighbor atoms and even medium-range order on length scale longer than the nearest neighbor to several nm, by the traditional diffraction and imaging techniques, long-range structure order in a glass has not yet been discovered before. In the Ce75Al25 metallic glass (MG), however, we discovered a long-range topological order corresponding to a single crystal of indefinite length. Structural examinations (e.g. high-resolution transmission electron microscopy, electron diffraction, X-ray diffraction) confirm that the MG is truly amorphous, isotropic, and unstrained, yet under 25 gigapascals hydrostatic pressures, every segment of a centimeter-length MG ribbon devitrifies independently into a face-centered cubic (fcc) crystal with the identical orientation. By using molecular dynamics simulations and synchrotron x-ray techniques, we elucidate that the mismatch between the large Ce and small Al atoms frustrates the crystallization and causes amorphization, but a long-range fcc topological order still exists. Pressure induces electronic transition in Ce, which eliminates the mismatch and manifests the topological order by the formation of a single crystal. The discovery directly links crystal and glass, the two extreme end-members of atomic structural orders. It brings new insight into the glass structure and may help to build more representative and reliable structural models for MGs.
9:45 AM - DDD3.02
A Phase-cut Method for Multi-species Kinetic Modeling: Sample Application to Nanoscale Defect Cluster Evolution in BCC Iron Following Helium Ion Implantation
Donghua Xu 1 Xunxiang Hu 2 Brian D Wirth 1 3
1Univ. of Tennessee Knoxville USA2Univ. of California Berkeley USA3Oak Ridge National Laboratory Oak Ridge USAShow Abstract
Many kinetic processes in materials involve clustering of multiple species, including microstructural damage induced by intense irradiation in nuclear fission and fusion environments. Solving rate equations for concentrations of all compositions throughout the multi-species phase space can readily become formidable when significant cluster growth occurs. Here, using nanoscale defect cluster evolution in BCC iron following helium ion implantation as an example, we demonstrate a phase-cut method that can effectively reduce this widely encountered problem. The method cuts out unnecessary compositions in the phase space and hence is much more efficient than a full-phase-space calculation. Yet it retains the same precision in predicted experimental observables. The cutting of phase space does not require an accurate nucleation and growth path be known a priori. The method may be applicable to other multi-species kinetic phenomena driven by irradiation and/or thermal annealing.
10:00 AM - DDD3.03
Analyzing He Irradiation Effects on Gold Twist Boundaries by STEM
Sanchita Dey 1 Patricia Abellan 2 Danny J. Edwards 3 Amit Misra 4 Nigel D. Browning 1 2
1Univ. of California, Davis Davis USA2Pacific Northwest National Laboratory Richland USA3Pacific Northwest National Laboratory Richland USA4Los Alamos National Laboratory Los Alamos USAShow Abstract
The effect of helium (He) implantation in structural materials and its interaction with the materials defects has been the subject of a wide number of studies [1, 2]. A recent publication on helium bubble formation in gold twist boundaries reported preferential He bubble formation at the nodes of screw dislocation networks . This is a promising result, which suggests that grain boundaries could be engineered by varying parameters such as the twist angle, for controlling radiation damage evolution.
Typically, a Transmission Electron Microscope (TEM) is used to investigate grain boundary structure, i.e., types of dislocation cores, distance between dislocation cores, Burgers vector, or the presence of a foreign material. For the case of He irradiated grain boundaries, “in-focus” imaging of small voids and bubbles in the TEM (diameter < 5nm) embedded in a comparatively thick specimen is difficult, due to the intrinsically low contrast of this system . Visualization of bubbles is typically achieved under objective lens underfocus values of approximately 1000nm [4, 5], with the subsequent loss of resolving power and limitations to the information that can be gained. There are also additional factors that make interpretation of TEM contrast in the case of He-irradiated grain boundaries studies even more difficult. First, in most cases the implantation depth - and thus the region of interest - will be 10&’s of nm, resulting in rather thick TEM foils (i.e. ~100nm). Also, the contrast from dislocations in grain boundaries may be very similar to that seen for bubbles. A different approach is thus needed. In this work, a 22.5KeV He ion irradiated Au bi-crystal has been investigated by STEM. Sample preparation was done following a procedure that avoids additional ion bombarding or mechanical thinning that could interfere with our STEM images interpretation. The optimal experimental conditions to observed He bubbles (~3nm size) in a 80nm thick foil (two 40 nm (001) Au films) Au twist boundary using Z-contrast imaging were investigated.
The research is part of the Chemical Imaging Initiative at Pacific Northwest National Laboratory. It was conducted under the Laboratory Directed Research and Development Program at PNNL, a multiprogram national laboratory operated by Battelle for the U.S. Department of Energy.
 M. Natasi et al., Philosophical Magazine 91, 553-573 (2011).
 A. Misra et al., JOM, 62-65 (2007).
 Z. Di et al., Phys. Rev. B 84, 052101 (2011).
 M.L. Jenkins and M.A. Kirk in: Characterization of radiation damage by TEM, Taylor & Francis (2000).
 M. Ruhle et al., Cryst. Lattice Defects 6, 129 (1975).
 K.J. Abrams et al., J. Appl. Phys. 111, 083527 (2012).
10:15 AM - DDD3.04
Pressure-induced Crystalline Phases Formed in Pure Amorphous Germanium after Full Unloading mdash; Evidence for a Rhombohedral r8 Phase
Bianca Haberl 1 Brett C Johnson 2 Sarita Deshmukh 1 Brad D Malone 3 Marvin L Cohen 3 Jeffrey C McCallum 2 Jim S Williams 1 Jodie E. Bradby 1
1Australian National University Canberra Australia2The University of Melbourne Melbourne Australia3University of California-Berkeley Berkeley USAShow Abstract
The considerable polymorphism of the elemental semiconductor germanium results in a complex phase diagram that has attracted wide interest in recent years [1-3]. For example on loading, diamond-cubic germanium (dc Ge) transforms to a metallic β-Sn structure and then through a series of further metallic phases as loading continues. Upon unloading, this β-Sn structure cannot transform back to dc Ge, but transforms instead to a number of crystalline metastable phases. Upon slow pressure release (in a diamond-anvil cell) the tetragonal st12 phase is formed, while upon rapid pressure release a bc8 structure is nucleated. This latter phase is not stable at room temperature and anneals to the hexagonal diamond (hex-Ge) phase within hours. Interestingly, no conclusive evidence of a rhombohedral structure (r8) has been observed for Ge although this phase is observed in the pressure regime between β-Sn and bc8 on unloading in silicon - a structurally analogous system.
In this work the pressure was applied by nanoindentation, where pointed diamond tips were used to induce highly localized pressure. To promote pressure-induced phase transformations amorphous germanium (a-Ge) films, formed by self-ion implantation into dc Ge, were used . Under the implantation conditions used in this study, thin (~2 mu;m), voidless, pure films are created. To account for the instability of the metastable phases, the samples were placed on dry ice immediately after indentation. The phase transformed regions were characterized using Raman microspectroscopy and then annealed at room temperature. The experimental Raman spectra were compared to density functional theory (DFT) simulations. The final (annealed) phases were also characterized using transmission electron microscopy.
Raman spectra taken immediately after indentation reveal a number of bands which mostly disappear within a few hours until solely hex-Ge is left. The presence of hex-Ge was confirmed by electron diffraction. The presence of this hex-Ge phase indicates that no st12 Ge was formed . Indeed, the DFT calculations show that the main Raman band observed in pristine indents cannot be matched to any phase other than r8. Comparison of such residual indents formed in a-Ge with those in silicon also suggest the presence of the r8 phase.
 G. J. Ackland, Rep. Prog. Phys. 64, 483 (2001).
 R.J. Nelmes et al., Phys. Rev. B 48, 9883 (1993).
 A. G. Lyapin et al., Phys.Stat.Solidi B 198, 481 (1996).
 D.J. Oliver et al., J. Appl. Lett. 106, 093509 (2009).
10:30 AM - DDD3.05
Carbon Nano Composite Fabrication and Characterization
Charles Payton 1 Cydale Smith 1
1AAMU University Normal USAShow Abstract
Glassy Polymeric Carbon (GPC) is as hard as diamond and can withstand temperatures up to 3000°C making it applicable for propulsion and thermal management systems in space and defence industries. GPC is a polymeric structure with Graphene ribbons dispersed throughout the matrix contributing to electrical characteristics which makes it suitable for high temperature applications. In our investigation GPC was heat treated in three stages up to 1000 °C from a phenolic resin precursor. After incorporating (GPC) with 1- 5 wt% Carbon Nano Tubes (CNT), thermal conductivity, electrical conductivity, and current voltage testing was done at a temperature range from 500°C to 1100 °C.
11:15 AM - DDD3.06
Crystalline Material with Amorphous Building Blocks: A Case of Long-range Ordered Amorphous Carbon Clusters
Lin Wang 1 2
1Carnegie Institution of Washington N.W. Washington USA2Jilin University Changchun ChinaShow Abstract
Solid-state materials can be categorized by their structure into crystalline (having periodic translation symmetry), amorphous (no periodic and orientational symmetry) and quasi-crystalline (having orientational but not periodic translation symmetry) phases. Hybridization of crystalline and amorphous structures at atomic level is of great interests, but hasn&’t been experimentally observed. Here, we report the discovery of a novel long-range ordered material constructed from units of amorphous carbon clusters which was synthesized by compressing solvated fullerenes (C60, C70). Using X-ray diffraction, Raman spectroscopy, and first-principles quantum molecular dynamics simulation, we observed that while fullerenes cages were crushed and became amorphous, the solvent molecules remained intact, playing a crucial role in maintaining the long-range periodicity. Once formed, the new high-pressure phase is quenchable back to ambient conditions and is ultra-incompressible with the ability to indent diamond. The discovery of such a unique phase has implications for the design and synthesis of new materials with novel characteristics.
11:30 AM - DDD3.07
The Formation of Extended Amorphous Hydrogenated Carbon Networks from the High Pressure Polymerization of Unsaturated Aromatic Hydrocarbons
Thomas C Fitzgibbons 1 John V Badding 1 Malcolm Guthrie 2 Stephen Davidowski 3 Jeffrey L Yarger 3
1Pennsylvania State University University Park USA2Carnegie Institution of Washington Washington USA3Arizona State University Tempe USAShow Abstract
Amorphous carbons have many energy applications ranging from solar cells to high surface area hydrogen storage substrates and ultrahigh strength lightweight building materials. Due to variable electronic, optical, and mechanical properties of carbon, which are dependent on the hybridization of the atoms, understanding how to create new carbon materials and how the properties of these materials change under extreme conditions is important to many fields including chemistry, physics, and materials science.
The room temperature reversibility between sp2 and sp3 hybridized carbon at high pressure observed in graphite and glassy carbon has stimulated research to investigate the effect that pressure has on the rehybridization of the molecular orbitals in small aromatic molecules. In addition to the reversible sp2 to sp3 transition, irreversible transitions in organic molecules to novel amorphous carbon networks are generating great interest. Throughout most of history the effect of pressure has not been investigated with regards to the reactivity of organic molecules. Initial studies have shown that the crosslinking of unsaturated organic molecules at high pressure and ambient temperature can lead to extended amorphous hydrogenated carbon networks with differing amounts of sp2 and sp3 carbon and hydrogen content. By determining trends and pathways in the reactivity of different hydrocarbons and examining the bonding present in the final amorphous product we are able to readily tune both the hydrogen content and sp2/sp3 carbon ratio of new carbon materials.
Our experiments are carried out in a diamond anvil cell, which due to diamond&’s high optical transparency and carbon being a low Z element allows for a myriad of in situ characterization techniques to be performed ranging from laboratory based vibrational spectroscopy to synchrotron based X-ray diffraction. Also because the resulting materials are recoverable to ambient conditions we have been able to take advantage of powerful analytical techniques ex situ, such as, multiwavelength Raman spectroscopy, FT-IR spectroscopy, transmission electron microscopy, X-ray diffraction, and neutron diffraction.
It has been established that at room temperature benzene undergoes an irreversible phase transition from a monoclinic crystal to an extended amorphous solid at 25 GPa. We present new details concerning the recovered product including structural information that has been acquired through neutron diffraction, Raman spectroscopy, and solid state NMR. The product is a colorless solid with a very high degree of sp3 bonded carbon. We have also investigated the high pressure amorphization of acene molecules: naphthalene, anthracene, and pentacene. The reactivity of each molecule was determined and the resulting amorphous networks were analyzed for differing sp3 content and relative crystallographic order.
11:45 AM - DDD3.08
Amorphous Diamond - A High-pressure Superhard Carbon Allotrope
Yu Lin 1 Li Zhang 2 Yuming Xiao 3 Paul Chow 3 Maria Baldini 4 Junyue Wang 4 Wenge Yang 4 Ho-kwang Mao 2 Wendy L Mao 1 5
1Stanford University Stanford USA2Carnegie Institution of Washington Washington USA3Geophysical Laboratory, Carnegie Institution of Washington Washington USA4Geophysical Laboratory, Carnegie Institution of Washington Washington USA5SLAC National Accelerator Laboratory Menlo Park USAShow Abstract
Compressing glassy carbon above 40 GPa, we have observed a new carbon allotrope with a fully sp3-bonded amorphous structure and diamond-like strength. Synchrotron x-ray Raman spectroscopy revealed a continuous pressure-induced sp2-to-sp3 bonding change, while x-ray diffraction confirmed the perseverance of non-crystallinity. Used as an indenter, the glassy carbon ball demonstrated exceptional strength by reaching 130 GPa with a confining pressure of 60 GPa. Such an extremely large stress difference of >70 GPa has never been observed in any material besides diamond, indicating the high hardness of this high-pressure carbon allotrope. The nanoscale transmission x-ray microscopy with 30 nm spatial resolution has enabled accurate pressure-volume determination of glassy carbon up to 40 GPa. The results provide guidance to understanding the mechanisms of the structure and bonding changes from glassy carbon to amorphous diamond. The transition is semi-reversible upon decompression revealed by these combined techniques.
12:00 PM - DDD3.09
Supercritical Fluid Electrochemistry: Advances in Understanding and Thin Film Formation
Charlie Yianni Cummings 1 Jie Ke 2 Michael George 2 Phil Bartlett 1
1University of Southampton Southampton United Kingdom2University of Nottingham Nottingham United KingdomShow Abstract
There is substantial interested in the use of supercritical fluids for the formation of next generation devices in material science. Supercritical fluids have the inherent advantages over conventional solvents in that they exhibit a low surface tension and an enhanced mass transport. These properties have led to the use of supercritical fluids to create small dimension, high aspect ratio structures which have applications in sensors, electronics and optical devices. Currently, there are two established techniques to form materials which are either reactive supercritical fluid deposition  or supercritical fluid electrodeposition .
Supercritical fluid electrodeposition has the inherent advantage over reactive supercritical fluid deposition in that the chemistry is highly controllable at the area of interest (ca. working electrode). This enhances material minimization as well as controlling parameters such as thickness to a high level of precision. Despite this there are a number of outstanding challenges yet to be addressed. Appropriate supercritical fluids must be selected as this needs to be optimized for the solubility of electrolytes/precursors as well as the available electrochemical window. Suitable stable supporting electrolytes must be chosen so that they dissolve and disassociate to increase the conductivity of the fluid. Precursors must be used with the intention of readily decomposing with minimal impurity contamination.
The SCFED Project (www.scfed.net) is a multidisciplinary collaboration of British universities investigating the fundamental and applied aspects of supercritical fluids. Previous work within the group has investigated various phase behavior and conductivity of electrolytes in supercritical fluids . As well as investigating the bulk and template electrodeposition of metals from supercritical fluids .
The electrodeposition of germanium was reported recently . Here, germanium films were electrodeposited from supercritical difluoromethame at a large overpotential. It is the purpose of this talk to elaborate the mechanism behind this process as well as present fundamental investigations. Data presented on supercritical fluid electrochemistry as well as dichloromethane electrochemically (as a non-aqueous liquid analogue) will be shown.
 A. H. Romang and J. J. Watkins, Chem Rev 2010, 110, 459
 J. Ke, W., Su, S. M. Howdle, M. W. George, D. Cook, M. Perdjon-Abel, P. N. Bartlett, W. Zhangm, F. Cheng, W. Levason, G. Reid, J. Hyde, J. Wilson, D. C. Smith, K. Mallik, P. Sazio, PNAS 2009 106, 14768-14772.
 P. N. Bartlett, D. Cook, M. W. George, J. Ke, W. Levason, G. Reid, W. Sub, W. Zhanga Phys. Chem. Chem. Phys., 2011, 13, 190-198
 J. Ke, P. N. Bartlett, D. Cook, T. L. Easun, M. W. George, W. Levason, G. Reid, D. Smith, W. Su W. Zhang Phys. Chem. Chem. Phys., 2012, 14, 1517-1528
12:15 PM - DDD3.10
Investigations of TiO2 Nanoparticles Surface-doped with Eu in Aqueous Fluids to High P-T Conditions
Phillip Aron McCart 1 Laurel Farris 1 Robert A Mayanovic 1 Hao Yan 1
1Missouri State University Springfield USAShow Abstract
Photocatalysts are useful for converting sunlight into renewable energy and for decomposition of organic waste products. Previous investigations indicate that TiO2 has potential for use in photocatalysis and for solar cell applications. The catalytic activity of TiO2 nanoparticles (NPs) is enhanced on the nanoscale due to the increase in the ratio of surface area to volume. The aim of our research is to further enhance the catalytic activity through modification of the surface due to the chemisorption of transition metal ions on TiO2 nanoparticles (NPs). A hydrothermal reactor was used to react anatase TiO2 nanoparticles (~ 13 nm across) with Eu3+ ions in aqueous fluids having pH values of 4.3 and 7.1 to 370 °C and approximately 30 MPa. XRD and Raman measurements made both before and after hydrothermal treatment with Eu shows that the overall anatase phase of the TiO2 NPs is preserved. However, Eu L3 edge EXAFS measurements indicate that the structure at the surface of the TiO2 nanoparticles undergoes distortion towards the rutile phase in the vicinity of adsorbed Eu. SEM imaging, combined with XRD indicates that the size and overall morphology of the TiO2 nanoparticles is preserved subsequent to hydrothermal treatment in the presence of Eu. The photoluminescence features occurring in the 500 to ~650 nm range are reduced in intensity for the TiO2 NPs hydrothermally reacted with Eu. Raman spectra show an overall reduction in the intensity of the primary bands in the Stokes region to 700 cm-1. The Eg(I) band (141 cm-1) is shifted by 2.2-3.4 cm-1 to higher wavenumbers for the TiO2 nanoparticles reacted with Eu at pH of 7.1 but not in a solution with pH value of 4.3.
12:30 PM - *DDD3.11
Dielectric Properties of Water under Pressure and Solubility of Minerals in the Earthrsquo;s Mantle
Ding Pan 1 Leonardo Spanu 1 Brandon Harrison 2 Dimitri Sverjensky 2 Giulia Galli 1 3
1UC Davis Davis USA2Johns Hopkins University Baltimore USA3UC Davis Davis USAShow Abstract
Knowledge of the dielectric constant of water as a function of pressure (P) and temperature (T) plays a critical role in understanding the chemistry of aqueous fluids in the Earth mantle. By using ab initio molecular dynamics, we computed the dielectric constant of water (ε0) under conditions of the Earth&’s upper mantle, predicting values in a regime beyond the reach of current experiments. We found that changes in the molecular dipole moment and hydrogen bond network upon compression strongly affect the dielectric constant of the liquid. Such changes are not accounted for by classical potentials, which yield values of ε0 substantially different from those of ab initio simulations. Based on the predicted dielectric constants, the solubility products of carbonate minerals were computed. We found that at P ~ 10 GPa and T = 1000 K, MgCO3 (magnesite) is at least slightly soluble in water at the millimolal level. This result suggests that water in the Earth&’s mantle has the capacity to store and transport significant quantities of oxidized carbon, leading to the hypothesis that some of the carbon stored in the deep Earth may be brought to the lithosphere by a flux of water associated with devolatilization reactions in subduction zones.
Brent Fultz, California Institute of Technology
Giulia Galli, University of California Davis
Malcolm Guthrie, Carnegie Institution of Washington
Chi-Chang Kao, Stanford Synchrotron Radiation Lightsource
Symposium Support Efree, a DOE-funded Energy Frontier Center
DDD6: Manipulating Structure and Properties from Nano to Mesoscale
Thursday AM, April 04, 2013
Marriott Marquis, Yerba Buena Level, Nob Hill AB
9:45 AM - *DDD6.01
Synthesis and Processing of Energy-relevant Ultra-hard Materials at High Pressure and Temperature
Yingwei Fei 1
1Carnegie Institution of Washington Washington USAShow Abstract
High-pressure synthesis has revolutionized the diamond industrial and it continues to play important roles in searching for new super-hard materials. It has been demonstrated that pressure can enhance materials properties and lead to new phenomena and novel physical properties, which may be utilized to advance technology and design new materials. However, pressure is generally an underutilized variable in materials synthesis and processing, particularly in synthesis of nanoscale materials and design of materials with enhanced properties. We have started to explore the role of pressure in materials synthesis. We have successfully synthesized the first stishovite (a high-pressure form of silica) nanocrystals in multi-anvil high-pressure device and new periodic crystalline mesoporous materials through high-pressure synthesis. We have also been exploring the layering structure of graphane at high pressure and new high-pressure synthesis pathways for other energy-relevant ultra-hard materials.
The Geophysical Laboratory is equipped with a range of high-pressure and high-temperature devices for materials synthesis, including piston-cylinder apparatus, multi-anvil device, and diamond-anvil cell. They provide complementary capabilities in achieving high pressure, sample size, and temperature stability. For large-volume materials synthesis in the multi-anvil device, we have replaced conventional tungsten carbide anvil with diamond composite anvil to achieve higher pressure with optimized sample volume. The improved performance increases the sample volume by at least ten-fold under extreme conditions. For controlled temperature synthesis in the diamond-anvil cell, we have focused on sample chamber design and internal resistant heater circuit on the anvil for improved heating stability and uniformity by using FIB (focus ion beam) milling technology. These improvements have greatly extended the capability of materials synthesis under extreme conditions. The combined capabilities with in-situ synchrotron X-ray diffraction and spectroscopic measurements and ex-situ characterization with high-resolution analytical tools provide new ways to examine materials properties and synthesis processing at high pressure, leading to novel applications.
10:15 AM - DDD6.03
Synthesis of Mesoporous Diamonds
Manik Mandal 1 Yingwei Fei 2 Kai Landskron 1
1Lehigh University Bethlehem USA2Carnegie Institution of Washington Washington USAShow Abstract
Mesoporos diamonds were synthesized by high pressure and high temperature treatment of a mesoporous carbon precursor. The mesoporous carbon was synthesized through soft-assembly of Pluronic F127 block copolymers as structure directing agents and resorcinol-formaldehyde as carbon precursor. The product material became optically transparent after treatment of carbon precursor at a pressure of 21 GPa and temperature of 1300 oC. The XRD pattern of the product material confirmed the formation of diamonds. Transmission electron microscopy (TEM) showed that the diamonds are porous and pore sizes are in the range of ~ 2-3 nm. Selected area electron diffraction showed that the synthesized diamonds are nano-crystalline. High-resolution TEM clearly showed the lattice spacing of diamonds.
10:30 AM - DDD6.04
Very High Laser-damage Threshold of Polymer-derived Si(B)CN-carbon Nanotube Composite Coatings
Romil Bhandavat 1 Ari Feldman 2 John Lehman 2 Chris Cromer 2 Gurpreet Singh 1
1Kansas State University Manhattan USA2National Institute of Standards and Technology Boulder USAShow Abstract
We study the laser irradiance behavior and resulting structural evolution of polymer-derived silicon-boron-carbonitride (Si(B)CN) functionalized multiwall carbon nanotube (MWCNT) coatings. We report a damage threshold value of 15 kWcm-2 and an optical absorbance of 0.97 after irradiation. This is an order of magnitude improvement over MWCNT (1.4 kWcm-2, 0.76), SWCNT (0.8 kWcm-2, 0.65) and carbon paint (0.1 kWcm-2, 0.87) based coatings tested at 2.5 kW CO2 laser at 10.6 µm wavelength. Electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy suggests partial oxidation of Si(B)CN forming a stable protective SiO2 phase upon irradiation. Coating's high damage tolerance and uniform absorbance is collectively attributed to the presence of carbon nanotubes and high oxidation resistance of amorphous Si(B)CN ceramic.
11:15 AM - DDD6.05
Silver Tantalate as a Novel High-temperature Solid Lubricant
Ashlie Martini 1 Hongyu Gao 1 Thomas Scharf 2 Samir Aouadi 2
1University of California Merced Merced USA2University of North Texas Denton USAShow Abstract
Silver tantalate (AgTaO3) exhibits extremely low friction and wear while sliding at high temperatures (measured up to 750°C) where most solid lubricants and coatings fail. This amazing functionality is thought to be enabled by the material&’s inherent combination of rigidity provided by a tantalum oxide backbone and lubricity provided by near-surface nanoclusters of silver. However, the exact mechanism by which the material functions is still unknown; this lack of understanding precludes further tailoring at the microscale to optimize performance. To address this issue, we use molecular dynamics simulation complemented by experimental friction measurements and microstructural characterization to investigate AgTaO3 in sliding contact under a range of temperature and loading conditions. Both simulations and experiments show that friction decreases with increasing temperature reaching ultra-low values at the highest temperatures studied. To understand this trend, we characterize the evolution of the crystallographic structure and composition of the shear planes. The results indicate that high temperatures induce structural phase transformations and atomic migration which enable the material to adapt to extreme environmental conditions. These results provide insight into the atomic-scale mechanisms underlying solid lubrication, particular that of binary layered metal oxides, at very high temperatures.
11:30 AM - DDD6.06
Supersonic Nanotechnology: Forming Ultrastrong Novel chi;-phase of Nylon 6 in a 50 nm Confinement
Alexander L. Yarin 1 Suman Sinha Ray 1 Min Wook Lee 2 Sam S. Yoon 2 Behnam Pourdeyhimi 3
1University of Illinois at Chicago Chicago USA2Korea University Seoul Republic of Korea3North Carolina State University Raleigh USAShow Abstract
Supersonic solution blowing, a novel process introduced in the present work, can produce strongly confined nanostructures resulting in an ultrastrong phase. In particular, we produced ultrastrong nylon 6 nanofibers in the 50 nm size range using a scalable process. In the electrically-assisted supersonic solution blowing, nylon 6 undergoes extreme stretching with the rate of stretching of the order of 1010 s-1 which is higher than in electrospinning by 7 orders of magnitude. This results in ultrastrong nylon 6 nanofibers of about 50 nm in cross-section. Using SEM, TEM, X-ray diffraction, differential scanning calorimetry (DSC) and micro-Raman spectroscopy, it is shown that the crystal structure in such nanofibers differs from the known stable α- and γ-phases, as well as from the metastable#61472;β- and δ-, and lambda;#61485;phases, representing itself as a novel chi;-phase. The X-ray diffraction pattern clearly showed smaller d-spacing than in the known crystals. The Raman spectroscopy revealed that the new chi;-phase is characterized by the diminution of CH2 stretching and a shift of -NH stretch. This clearly shows that the chi;-phase results from an enormous cross-sectional squeezing. A simple theoretical model has been proposed to describe the process. Also, a ten-fold increase in Young&’s modulus of the novel chi;-phase compared to the ordinary α-phase was revealed by nanoindentation of a single nanofiber.
11:45 AM - DDD6.07
Ring Opening Metathesis Polymerization Route to Low Density Polymeric Aerogel Coatings on Non-planar Substrates and Its Doping with a High z Atoms
Sung Ho Kim 1 Christoph Dawedeit 1 Tom Braun 1 Jeremy Lenhardt 1 Carlos Valdez 1 Swanee Shin 1 Marcus Worsley 1 Sergei Kucheyev 1 Kuang Jen Wu 1 Juergen Biener 1 Joe Satcher 1 Alex Hamza 1
1Lawrence Livermore National Laboratory Livermore USAShow Abstract
Simple and versatile approach to low density polymeric aerogel coatings on non-planar substrates was explored from ring opening metathesis polymerization (ROMP) approach to copolymerize dicyclopentadiene (DCPD) with norbornene-based monomers (NB-R) employing a Grubbs&’ Ruthenium-based catalyst. First, we investigated the effect of crosslinking in the polymer backbone on the uniformity of the gel coatings formed under shear by either adding a multi-norbornene based crosslinker ((NB)n-R) to increase, or linear NB-R co-monomers to decrease, the degree of crosslinking, respectively. We observed that adding linear monomers dramatically improved the uniformity of the gel films, which we attribute to cross-linking induced changes in the rheological properties at the gel point. Second, the copolymerization of DCPD and NB-R with a different pendant group also causes a significant change in the morphology of PDCPD-based aerogels by modifying lengths of strands in the fibrous polymer network. The effect of NB-R addition on the pore structure of the aerogels is discussed in context of a molecular and interparticle crosslinking model. Finally, several methods to dope aerogels with several high z elements will be presented and discussed. Our results highlight the potential of the ROMP-based copolymerization approach as a facile and versatile route to functionalized low density polymeric aerogels.
12:00 PM - DDD6.08
A Zeolitic lsquo;Chatterboxrsquo;: Pressure-induced Hydration and Structural Inversions in Natrolites
Donghoon Seoung 1 Yongmoon Lee 1 Chi-Chang Kao 2 Thomas Vogt 3 Yongjae Lee 1
1Yonsei University Seoul Republic of Korea2SLAC National Accelerator Laboratory Menlo Park USA3University of South Carolina Columbia USAShow Abstract
High-pressure synchrotron X-ray powder diffraction studies of a series of monovalent cation-exchanged natrolites, A16Al16Si24O80 x nH2O (A= Li, Ag, K, Na, Rb and Cs and n=14, 16, 22, 24, 32) in the presence of water, reveal structural changes that exceed by far what can be achieved by varying temperature and/or chemical composition. The degree of volume expansion caused by pressure-induced hydration (PIH) is established to be inversely proportional to the non-framework cation radius. The expansion of the unit cell volume via PIH is as large as 20.6% in Li-natrolite at 1.0 GPa and decreases to 6.7%, 4.8%, 3.8%, and 0.3% in Na-, Ag-, K-, and Rb-natrolites, respectively. On the other hand, the onset pressure of PIH is set as low as 0.4 GPa in Ag-natrolite and appears to increase with non-framework cation radius to 2.0 GPa in Rb-natrolite. In Cs-natrolite no PIH is observed but a new phase forms at 0.3 GPa with a 4.8% contracted unit cell and different cation-water configuration in the pores. In K-natrolite, the elliptical channel undergoes a unique overturn upon the formation of super-hydrated K16Al16Si24O80 x 32 H2O at 1.0 GPa, which reverts back above 2.5 GPa as the potassium ions interchange their locations with those of water and migrate from the hinge to the center of the pores. We use a simple ‘chatterbox origami&’ model to account for the observed guest-host arrangements in natrolites under pressure. Pressure thus provides numerous opportunities to expand and modify known chemical and physical properties of small-pore zeolites, which is evidenced by pressure-induced insertion of CO2 into the ‘nominally non-penetrating&’ natrolite channel.
12:15 PM - DDD6.09
Detonation Nanodiamond: Synthesis, Properties, and Applications
Vadym Mochalin 1
1Drexel University Philadelphia USAShow Abstract
Nanodiamond powder produced by detonation synthesis is one of the most promising materials for advanced nanocomposites and biomedical applications . It also can be used for separation and catalysis and is a commercially viable precursor for carbon nanoonions - material for high power micrometer size electrochemical double layer capacitors and potentially, Li-ion batteries. The material is produced by detonation of explosives with negative oxygen balance in oxygen deficient atmosphere of a closed chamber, where extremely high pressures and temperatures develop during detonation. Nanodiamond consists of diamond particles of ~5 nm in diameter, combining fully accessible surface of 300 - 400 m2/g with a rich and tailorable surface chemistry. Nanodiamond has unique properties including optical, electrical, thermal, and mechanical ones, and is biocompatible and non-toxic material. Due to numerous functional groups attached to its surface ND has noticeable catalytic and electrochemical activity and can be used as a material for red-ox electrodes.
Heating nanodiamond in vacuum or inert gas at high temperatures results in progressive graphitization, yielding carbon nanoonions - a material, which is composed of spherical particles ~ 5 nm in diameter made of concentric graphene spheres, resembling the structure of an onion. Carbon nanoonions have small particle size, high curvature, large and fully accessible surface, and, in contrast to nanodiamond, are electrically conductive. These properties make them a material of choice for high power supercapacitors, electrically conductive additives for battery electrodes, composite materials for electromagnetic shielding, and other applications.
Synthesis, properties, and some representative applications of nanodiamond and carbon nanoonions in energy storage, composites, biomedical imaging, and drug delivery will be discussed.
1. Mochalin, V. N.; Shenderova, O.; Ho, D.; Gogotsi, Y. Nature Nanotechnology, 2012, 7, 11-23
12:30 PM - *DDD6.10
Synthesis and Characterization of an Ultrananocrystalline Diamond Aerogel
Peter J. Pauzauskie 1 Jonathan C. Crowhurst 2 Marcus A. Worsley 2 Ted A. Laurence 2 Yinmin Wang 2 David Kilcoyne 3 Sirine Fakra 3 Peter Weber 2 Joe H. Satcher 2
1University of Washington Seattle USA2Lawrence Livermore National Laboratory Livermore USA3Lawrence Berkeley National Laboratory Berkeley USAShow Abstract
High-surface-area mesostructured carbon materials have attracted a great amount attention in recent years because of a growing number of applications in energy storage, chemical catalysis, separations, and sensing. In particular, amorphous carbon aerogels have attracted much interest since the 1980's due to their low density, large intrinsic surface areas (>1000 m^2/g), large pore volume, low dielectric constant, and high strength. In this talk we present the use of high-pressure (~20 GPa) laser-heating (>1500°C) within a diamond anvil cell (DAC) to convert the amorphous network of a low-density (40 mg/cc) carbon aerogel into an ultrananocrystalline diamond aerogel. Raman spectroscopy is used to probe the amorphous-to-diamond phase transition at pressure within the DAC. High-resolution transmission electron microscopy images of recovered material indicate diamond crystallite sizes range from 1 to 100 nm, with electron diffraction and electron energy loss confirming the presence of the diamond phase. Photoluminescence spectroscopy and confocal time-correlated single-photon counting indicate the recovered material contains both negatively-charged and neutral nitrogen-vacancy (NV) complexes. Synchrotron scanning transmission x-ray microscopy (STXM) is used to compare the carbon electronic density-of-states of the amorphous starting material with the recovered diamond aerogel with ~100 meV energy resolution. Finally, we use nanoscale secondary ion mass spectrometry to investigate doping of the resorcinol-formaldehyde starting material with the aim of chemically tuning heteroatomic point defects within this diamond material system.