Electronic, optical, elastic, mechanical and vibrational properties of hexagonal h-ZnS with density functional theory

Abstract

In this work, we explored the electronic, optical, elastic and phonon effect in two-dimensional hexagonal Zinc Sulphide (h-ZnS) monolayer. We investigated which aspects of the orbitals of Zinc and Sulphur are the sources of core levels, valence band level and conduction band level in the bandstructure. We wrote the optical parameters in terms of dielectric functions. We observed that the absorption peak represents the optical bandgap. Using the linear response scheme, we determined the phonon dispersions and noticed the transverse-acoustic is the main source in precisely describing the phase transition from the bulk ZnS to h-ZnS monolayer. We also report that h-ZnS has a direct bandgap of 2.58 eV and the material is brittle, based on the B/G ratio. We notice, however, the elastic constants of the h-ZnS are somewhat different from the bulk. We further report that the use of the hybrid functionals is significant, while computationally demanding, in estimating the electronic bandstructure, compared to PBE-GGA, which overestimates the c axis and underestimates an axis.