Finite-temperature molecular-dynamics study of unstable stacking fault free energies in silicon

We calculate the free energies of unstable stacking fault (USF) configurati ons on the glide and shuffle slip planes in silicon as a function of temper ature, using the recently developed environment-dependent interatomic poten tial (EDIP). We employ the molecular dynamics (MD) adiabatic switching meth od with appropriate periodic boundary conditions and restrictions to atomic motion that guarantee stability and include volume relaxation of the USF c onfigurations perpendicular to the slip plane. Our MD results using the EDI P model agree fairly well with earlier first-principles estimates for the t ransition from shuffle to glide plane dominance as a function of temperatur e. We use these results to make contact to brittle-ductile transition model s. [S0163-1829(98)06043-3].