TIGHT-BINDING STUDIES OF CRYSTALLINE SI1-XGEX ALLOYS

Lattice constants and bond lengths in crystalline Si1-xGex alloys are calculated by the bond orbital model and radial force model. The resul ts are compared with theoretical results obtained by the valence force -field model calculation and experimental results obtained by x-ray di ffraction and extendeded x-ray absorption fine-structure measurements, and are found to be in good agreement with experiments. The trends in elastic constants and electronic band structure as functions of compo sition x are obtained in the simple virtual-crystal approximation.