Torsional moduli of transition metal dichalcogenide nanotubes from first principles

TL;DR

This study uses ab initio DFT calculations to determine the torsional moduli of transition metal dichalcogenide nanotubes, revealing their dependence on diameter and composition, and proposing a predictive linear model.

Contribution

It provides the first systematic DFT-based analysis of torsional moduli in TMD nanotubes, including a predictive model based on bond characteristics.

Findings

Torsional moduli follow a trend: MS₂ > MSe₂ > MTe₂.

Moduli scale approximately with the cube of the diameter.

The linear regression model accurately predicts torsional moduli based on bond properties.

Abstract

We calculate the torsional moduli of single-walled transition metal dichalcogenide (TMD) nanotubes using ab initio density functional theory (DFT). Specifically, considering forty-five select TMD nanotubes, we perform symmetry-adapted DFT calculations to calculate the torsional moduli for the armchair and zigzag variants of these materials in the low-twist regime and at practically relevant diameters. We find that the torsional moduli follow the trend: MS$_2$ $>$ MSe$_2$ $>$ MTe$_2$. In addition, the moduli display a power law dependence on diameter, with the scaling generally close to cubic, as predicted by the isotropic elastic continuum model. In particular, the shear moduli so computed are in good agreement with those predicted by the isotropic relation in terms of the Young's modulus and Poisson's ratio, both of which are also calculated using symmetry-adapted DFT. Finally, we develop a linear regression model for the torsional moduli of TMD nanotubes based on the nature/characteristics of the metal-chalcogen bond, and show that it is capable of making reasonably accurate predictions.