High-pressure phase transformation and elastic behavior of XC (X = Si, Ge, Sn and Pt) compounds

Pressure-induced structural aspects of ZnS-type (B3) to NaCl-type (B1) structure in XC (X = Si, Ge, Sn and Pt) compounds are presented. An effective interionic interaction potential with long-range Coulomb, van der Waals (vdW) interaction and the short-range repulsive interaction up to second-neighbor ions within the Hafemeister and Flygare approach with modified ionic charge is developed. Particular attention is devoted to evaluate the vdW coefficients following the Slater–Kirkwood variational method, as both the ions are polarizable. Our results on vast volume discontinuity in pressure volume phase diagram identify the structural phase transition from B3 to B1 structure. The estimated value of the phase transition pressure (Pt) and the magnitude of the discontinuity in volume at the transition pressure are consistent as compared to the reported data. The variations of elastic constants with pressure follow a systematic trend identical to that observed in other compounds of ZnS and NaCl-type structure family and the Born relative stability criteria are valid in XC compounds. (paper)