Ab initiocalculation of phonon dispersions in II-VI semiconductors

The vibrational properties of ZnSe, ZnTe, CdSe, and CdTe are determined by density-functional perturbation theory. To this end we have generalized this method so as to explicitly account for the nonlinear core correction to the exchange and correlation energy of systems treated with pseudopotentials. Furthermore, we have implemented a method to enhance the transferability of pseudopotentials of group-II atoms with shallow d electrons frozen in the core. The accuracy obtained in this way is similar to that previously achieved for elemental and III-V semiconductors.