ENERGETICS AND ELECTRONIC-STRUCTURE OF THE HYPOTHETICAL CUBIC ZINCBLENDE FORM OF GEC

We have peformed the first ab-initio investigation of the hypothetical IV-IV compound GeC with zincblende structure, and have compared its properties with those of SiC. The calculations are performed using a planewave expansion within the local density approximation and the pseudopotential approximation. It is found that GeC, like SiC, is a wide-gap semiconductor with an indirect bandgap. Unlike SiC, we find that GeC is thermodynamically unstable toward decomposition into its segregated components under zero pressure. However, it becomes significantly more stable under pressure up to the phase transition of Ge to the beta-tin structure. The effect of different choices of the form and generating scheme for the pseudopotential and the form for the correlation energy functional on the results of such calculations is also discussed.