Density functional and force field modeling of achiral multi-walled MX2 (M = W, Hf; X = S, Se) nanotubes

Abstract

The investigation of transition metal dichalcogenide nanotubes is characterized by significant variability. The majority of experimental studies on these materials focus on the structural and optical properties of MoS₂ and WS₂ multi-walled nanotubes (MWNTs). In contrast, research on WSe₂ nanotubes has received comparatively little attention. Only a limited number of studies have synthesized and explored the MWNTs based on HfS₂ and HfSe₂. Theoretical researches mainly include density functional theory (DFT) calculations for single-, double-, and triple-walled nanotubes with relatively small diameters. We propose new atomistic potentials designed to model the MWNTs based on W and Hf dichalcogenides, whose diameters approach the experimentally observed ones and are beyond the capabilities of ab initio methods. The developed force fields have been applied to the study of the structure and stability of achiral nanotubes, which are composed of 1–10 single-wall components. The properties of WX₂-based nanotubes are compared with those of analogous HfX₂-based nanotubes (X = S, Se). In particular, it has been shown that HfX₂ multi-walled nanotubes are much more faceted than similar WX₂ multi-walled nanotubes. The stability of multi-walled nanotubes with respect to single-wall components and nanolayers was investigated. For the first time, it has been found that the binding energy of achiral MWNTs is a linear function of the inverse wall number. The slope of the resulting line is related to the interwall adhesion energy.