Phase diagram of silicon by molecular dynamics.

Abstract

Using the Stillinger-Weber potential we explored the liquid, crystal, and amorphous phase diagram of silicon by molecular dynamics. We obtain the chemical potential of the crystal by following the crystal-vapor coexistence curve from the T=0 harmonic solid up to the melting point. The liquid free energy is found by reversible expansion. The thermodynamic melting point is 1691\ifmmode\pm\else\textpm\fi{}20 K, which is very close to the experimental value of 1683 K. Contrary to experiment, the calculated supercooled liquid phase does not undergo a first-order transition to the fourfold-coordinated amorphous structure upon cooling, since the chemical potentials of these structures are almost equal over a wide range of temperatures. Diffusion coefficients, heat capacities, and expansivities are compared with experiment.