Bonding Charge Density and Ultimate Strength of Monolayer Transition Metal Dichalcogenides

TL;DR

This study uses first-principles calculations to analyze how the chemical composition and electronic structure influence the mechanical strength and deformation behavior of monolayer transition metal dichalcogenides, revealing a linear relationship with charge transfer.

Contribution

It provides a detailed first-principles analysis of the mechanical response of monolayer TMDs, linking electronic structure to ultimate strength and deformation characteristics.

Findings

Ultimate strength varies with composition and loading direction.

Electronic state redistribution affects mechanical behavior.

Strength correlates linearly with charge transfer.

Abstract

Two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) can withstand a large deformation without fracture or inelastic relaxation, making them attractive for application in novel strain-engineered and flexible electronic and optoelectronic devices. In this study, we characterize the mechanical response of monolayer group VI TMDs to large elastic deformation using first-principles density functional theory calculations. We find that the ultimate strength and the overall stress response of these 2D materials is strongly influenced by their chemical composition and loading direction. We demonstrate that differences in the observed mechanical behavior can be attributed to the spatial redistribution of the occupied hybridized electronic states in the region between the transition metal atom and the chalcogens. In spite of the strong covalent bonding between the transition metal and the chalcogens, we find that a simple linear relationship can be established to describe the dependence of the mechanical strength on the charge transfer from the transition metal atom to the chalcogens.