Electronic, vibrational, and thermodynamic properties of ZnS with zinc-blende and rocksalt structure

We have measured the specific heat of zinc-blende ZnS for several isotopic compositions and over a broad temperature range (3\char21{}1100 K). We have compared these results with calculations based on ab initio electronic band structures, performed using both local-density approximation and generalized gradient approximation exchange-correlation functionals. We have compared the lattice dynamics obtained in this manner with experimental data and have calculated the one-phonon and two-phonon densities of states. We have also calculated mode-Gr\"uneisen parameters at a number of high-symmetry points of the Brillouin zone. The electronic part of our calculations has been used to investigate the effect of the $3d$ core electrons of zinc on the spin-orbit splitting of the top valence bands. The effect of these core electrons on the band structure of the rocksalt modification of ZnS is also discussed.