The structural properties of binary silicon-germanium alloys are investigated by means of large-scale constant-pressure Monte Carlo simulations of the Stillinger-Weber model. At low temperatures, the binary-mixture phase separates into Si-rich and Ge-rich phases. The two-phase coexistence region is terminated by a critical point that belongs to the mean-field universality class. We also studied the structural properties of pure Si and Ge as well as the binary mixture. In particular, we found that the linear thermal expansions for both Si and Ge are in agreement with experiments, and that Végard’s law is valid at temperatures above the critical point. Finally, we compare the bond-length and bond-angle distributions with earlier analytical and numerical calculations based on the Kirkwood potential.

• Received 21 November 1994

DOI:https://doi.org/10.1103/PhysRevB.51.4894