Unusual structural and electronic properties of SnxGe1-x alloys

First-principles pseudopotential plane-wave calculations are used to investigate the structural and electronic properties of cubic SnxGe1-x alloys. The studies focus on the determination of the variation of the lattice parameter and the optical band gap bowing of these alloys. An unusual behavior is found for the variation of the lattice parameter; in particular, a positive deviation from Vegard's law is found. This unusual feature is consistent with recent X-ray data. The calculated optical band gap bowing parameter is found to be strongly composition dependent. At x = 0.125, the calculated bowing parameter is in good agreement with experiment. It is shown that both structural and chemical effects are important for this material. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.