Bondlengths and phase stability of silicon-germanium alloys under pressure

Bondlengths of Si-Si, Si-Ge, and Ge-Ge pairs in Silicon-Germanium alloys were determined as a function of hydrostatic pressure using ab initio electronic structure calculations. A series of ordered structures was selected to represent the various atomic environments in actual alloys. Enthalpies of formation computed for these structures were used to model the phase stability under hydrostatic pressure.