Effects of Temperature Induced Phase Transition in Bulk CdS Structures

We perform ab initio calculations to study the electronic and phonon properties of bulk CdS for wurtzite (wz) and zinc blende (zb) phases. The density of states and bandstructure suggest that CdS acts like a direct bandgap semiconductor with a bandgap of ~ 1 eV for both the phases. We find that both the phases experience LO-TO splitting and show peaks for multiple phonon frequencies across the phonon spectrum. We implement DFT coupled with quasi harmonic approximation (QHA) to calculate the Gibbs free energy at 0 GPa for a temperature range (0 to 2200) K. We infer that under ambient conditions (285 to 300) K wz-CdS phase is stable, while at low temperature conditions both the phases exhibit similar properties. We predict a possible phase transition from zb to wz at 200 K.