Systematic investigations of the electron, phonon, elastic and thermal properties of monolayer so-MoS2 by first-principles calculations

Abstract

Abstract For the research of Transition Metal Dichalcogenides (TMDCs), the predecessors have already involved a lot. However, the research of the two-dimensional square-octagon MoS2 (so-MoS2) with elastic and thermal properties are not enough. Here, we have investigated the electronic, phonon, elastic and thermal properties of the primitive monolayer so-MoS2 by first-principles calculations and theoretical analysis. Firstly, The Dirac point exists on its band structure and mainly contributed by d orbits of Mo atoms, it will open the energy gap and enter the insulating phase when the spin–orbit coupling is added. Secondly, the phonon spectrum indicates that so-MoS2 is dynamically stable. The Raman, infrared active modes were also studied. Thirdly, we investigated the elastic constants of monolayer so-MoS2 by the nonlinear least-squares fitted the relation between energy density and strain. We find monolayer so-MoS2 has better flexibility than other two-dimensional materials, such as, monolayer MoS2. Moreover, we investigated the elastic properties of twisted and strained so-MoS2 and it is found that twisting and straining have little effect on the elasticity of monolayer so-MoS2 and they are all elastic isotropic. Finally, the thermodynamic properties of the Gruneisen parameter, thermal expansion coefficient, CV, entropy and lattice thermal conductivity of monolayer so-MoS2 were also studied. We used two methods of grun and phonopy-qha to analyze Gruneisen parameter and Thermal expansion coefficient, and find phonopy-qha method is better and more common. The study from hexagonal honeycomb lattice monolayer MoS2 to square lattice monolayer so-MoS2, which broadens the promising topological material systems.