High pressure structural phase transitions in IV-VI semiconductors

We have studied high pressure structural phase transitions in lead chalcogenides by means of first principles total energy calculations within the generalized gradient approximation (GGA) using the full potential linear-muffin-tin-orbital (FPLMTO) method. These compounds are stable in the NaCl-type structure at ambient conditions and transform to the CsCl-type of structure under high pressure through an intermediate phase. The experimental data suggests that this intermediate phase could be either the TlI-type phase or the GeS-type phase. However this data was not enough to solve the full structural refinement. So we have performed fully relaxed total energy calculations to get the full structure of this intermediate phase. Our calculated transition pressures are in very good agreement with experiment.