TOTAL-ENERGY CALCULATION FOR CDXSN1-XTE

In the mixed crystal system CdxSn1-xTe, the transition from a ten-electron (x=0) to an eight-electron system (x=1) is realized, which is accompanied by a change in the crystal structure from rocksalt (SnTe) to zincblende (CdTe). The structure and lattice constants of solid solutions, grown (in part under high pressure) for nearly the whole mixing range, are known. We use norm-conserving pseudopotentials in connection with the local density and virtual crystal approximation for ab initio calculations of the stable crystal structure and the lattice constant in dependence on the composition x of the system. Our calculated results confirm Vegard's rule and give a crossover from rocksalt to zincblende at about x=0.9 in accordance with experimental data. The crossover is accompanied by a change in the binding character, which can be seen in a change of the electronic charge density.