Elastic properties of transition metal dichalcogenides

TL;DR

This study uses first-principles calculations to analyze the structural and elastic properties of transition metal dichalcogenides, revealing differences between metallic and semiconducting types and establishing trends based on composition.

Contribution

It provides a systematic first-principles comparison of the elastic properties of various 2H-MX$_2$ TMDs, highlighting the influence of electronic character and composition.

Findings

Metallic TMDs have larger in-plane lattice parameters.

Metallic TMDs exhibit lower in-plane stiffness and shear modulus.

Clear trends in mechanical moduli relate to atomic number and composition.

Abstract

We present a comprehensive first-principles study of the structural and elastic properties of 2H-MX$_2$ transition metal dichalcogenides (TMDs) (M = W, Mo, Ta, Nb; X = S, Se). Using density functional theory with various van der Waals exchange-correlation functionals, we systematically investigate the influence of nonlocal interactions on lattice parameters, elastic constants, and mechanical moduli. Our results reveal a fundamental distinction between semiconducting and metallic TMDs: metallic compounds exhibit larger in-plane lattice parameters and reduced interlayer spacing, consistent with their bonding characteristics. We find that metallic TMDs display significantly lower in-plane stiffness and shear modulus compared to their semiconducting counterparts. We discuss this behaviour in the context of the observed charge density waves. In addition, we establish clear trends in the bulk, Young's, and shear moduli, demonstrating the role of atomic number and chemical composition in determining mechanical stability.