The mechanical and thermal parameters of two-dimensional hexagonal materials evaluated using elastic properties: Monolayer MoS2 as an example

Abstract

The thermal expansion coefficient of two-dimensional (2D) materials is a very important physical parameter when forming heterostructures. Here, we have established a method that can be employed to evaluate the thermal expansion coefficient of 2D hexagonal materials by the computationally feasible elastic parameters, where the monolayer MoS2 is chosen as an example. Using the first-principles calculations, we calculate the elastic constants under different strains from the strain–stress relationship. Then, based on the calculated elastic parameters, the mechanical and thermal parameters of the monolayer MoS2, including bulk moduli, shear moduli, sound velocities, Debye temperature, heat capacity and thermal expansion coefficient, are obtained. The calculation results are in good agreement with those determined by quasi-harmonic phonon calculations and the experimental results. The monolayer WS2 is employed to further confirm the validity of the methodology. This method can also be widely used to investigate the thermal properties of other 2D materials and thin films.

Keywords

• Thermal parameters
• Elastic properties
• Monolayer MoS2
• First-principles calculations