Stability and Electronic Structure of Double-Walled Transition Metal Dichalcogenide Nanotubes

The groundbreaking discovery of a new class of materials, one-dimensional (1D) van der Waals (vdW) heterostructures [1], has opened the door for studying a range of novel physics, material properties, and exciting applications. With two dimensions in the sub 10 nm scale and near limitless material combinations of nanotube (NT) layers, 1D vdW heterostructures have demonstrated novel physics and material properties such as interlayer excitonic coupling [2], charge transfer, and importantly, tunable optoelectronic properties [3]. That layers in 1D vdW materials are connected via vdW forces alone highlights the need for a better understanding of the interactions between NT layers, and how it affects properties.<br/><br/>In this study density functional theory (DFT) and the density functional tight binding method GFN1-xTB were used to systematically investigate how vdW interactions between NT layers of transition metal dichalcogenide (TMD) double-walled (DW) NTs affect stability and electronic properties. The strength of vdW interactions were modulated by increasing the intertube separation gradually, and the stability, band structure, rotational and translational potential energy surfaces and vdW interaction energies were calculated using DFT and GFN1-xTB. It was found that the vdW forces have a stabilizing effect on DWNTs, and that the magnitude of the vdW forces depend on the chalcogenide, not the transition metal. The vdW interactions facilitate band gap changes of up to 0.3 eV, without changes to the tube chirality, due to radial compression of the inner-tube.<br/><br/><b>References</b><br/>[1] R. Xiang, et al., <i>Science</i>, 2020, <b>367</b>, 6477.<br/>[2] M.G. Burdanova, et al., <i>Advanced Functional Materials</i>, 2022, <b>32</b>, 11.<br/>[3] S. Cambré et al., <i>Small</i>, 2021, <b>17, </b>38.