Ab initio study on the electromechanical response of Janus transition metal dihalide nanotubes

TL;DR

This study uses density functional theory to analyze how Janus transition metal dihalide nanotubes' electronic properties, like bandgap and effective mass, respond to mechanical strains, revealing linear and quadratic dependencies.

Contribution

It provides the first detailed computational analysis of the electromechanical response of Janus TMH nanotubes, linking electronic changes to strain and atomic orbital contributions.

Findings

Bandgap decreases linearly with tensile strain.

Bandgap decreases quadratically with shear strain.

Effective mass of electrons increases while holes decrease under strain.

Abstract

We study the electronic response of Janus transition metal dihalide (TMH) nanotubes to mechanical deformations using Kohn-Sham density functional theory. Specifically, considering twelve armchair and zigzag Janus TMH nanotubes that are expected to be stable from the phonon analysis of flat monolayer counterparts, we first compute their equilibrium diameters and then determine the variation in bandgap and effective mass of charge carriers with the application of tensile and torsional deformations. We find that the nanotubes undergo a linear and quadratic decrease in bandgap with tensile and shear strain, respectively. In addition, there is a continual increase and decrease in the effective mass of electrons and holes, respectively. We show that for a given strain, the change in bandgap for the armchair nanotubes can be correlated with the transition metal's in-plane $d$ orbital's contribution to the projected density of states at the bottom of the conduction band.