Pressure induced structural phase transformations in lead chalcogenides

In this study, the pressure induced phase transformations of lead chalcogenides have been investigated using SIESTA package program. The studies were performed using the generalized gradient approximation (GGA) and the local density approximation (LDA) in the context of density functional theory (DFT). It was observed that the NaCl-type structures of the PbS and PbSe compounds transformed to the CsCl-type structures at 240 and 50 GPa pressures, respectively, using the GGA and the NaCl-type structures of PbS, PbSe and PbTe compounds transformed to CsCl-type structures under the pressure of 160, 50 and 30 GPa, respectively, using the LDA approximation. In order to investigate the comparable transition pressure with the experimental results, total energy and enthalpy calculations were carried out. According to these calculations, transformations of NaCl-type structures of PbS and PbSe to CsCl-type structures for GGA approximation were obtained at around 12 and 10 GPa, respectively. The transformations from NaCl-type structures of PbS, PbSe and PbTe to CsCl-type structures for LDA approximation were obtained at 10, 8 and 6.5 GPa, respectively. In all other approximation except for the GGA for the PbSe compound, it was seen that the initially NaCl-type structures of PbS, PbSe and PbTe were transformed to the CsCl-type structure following the formation of some intermediate phases.