Role of semicore electrons in the lattice dynamics of a cubic ZnS crystal

The phonon dispersion in a ZnS crystal has been studied by the density functional theory method with different pseudopotentials containing 10 (Zn$^{12+}$) and 18 (Zn$^{20+}$) semicore electrons of the shell with the principal quantum number $n$ = 3 in a zinc atom. It has been found that the pseudopotential of Zn$^{20+}$, unlike the pseudopotential of Zn$^{12+}$ describes the phonon dispersion more accurately. An analysis has demonstrated that, in this case, the degree of $d$–$p$ hybridization of semicore $d$ states of zinc with the valence $p$ states of sulfur decreases.