Muzi Chen1,Andrew Cairns1
Imperial College London1
Muzi Chen1,Andrew Cairns1
Imperial College London1
The prototypical rutile structure (TiO<sub>2</sub>, TeO<sub>2</sub>, etc.) has been shown to undergo a ferroelastic transformation from a tetragonal structure to the orthorhombic structure on compression or cooling. Following the ferroelastic transition, the structure shows negative linear compressibility (NLC) in one of the orthogonal directions. Negative linear compression (NLC) is the property of a material that refers to the phenomenon that when a system is uniformly compressed, it expands in at least one linear direction.<sup>1</sup> Material with negative compression properties has many promising applications in engineering, such as sensitive pressure sensing, actuators, and the development of artificial muscle—critically depends on the intrinsic NLC response. Therefore, we are interested in investigating whether this phenomenon occurs in its structural analogues.<br/><br/>In our work, we investigated the structural analogues to rutile, which are transition metal dicyanamide and tricyanomethanide systems, abbreviated as M(dca)<sub>2</sub> and M(tcm)<sub>2</sub> (M = Mn, Cu, Fe, Co, Ni, and Zn). Both variable-temperature diffraction and high-pressure diffraction were employed. Our results show significant negative thermal expansion (NTE) and negative linear compressibility (NLC) in a series of M(dca)<sub>2</sub> and M(tcm)<sub>2</sub> materials. The magnitude of thermal and pressure-induced structural changes in each case was proved to be affected by the transition metal size and Jahn Teller distortions.<br/>Reference:<br/>[1] Andrew B. Cairns and Andrew L. Goodwin. Negative linear compressibility. Phys. Chem. Chem. Phys., 17:20449–20465, 2015.