The crystallization of pure silicon has been simulated using Monte Carlo computer modeling. These are atomic scale simulations, which permit an examination of the relationship between the configuration of atoms at the interface and the local growth conditions. It is well known that silicon growing from its melt facets on the (1 1 1) face, which implies a nucleation barrier to growth. None of the other orientations facet, and the interface for these other orientations lies very close to the melting point isotherm. The relationship between the growth rate and undercooling has been modeled for the (1 0 0) and (1 1 1) faces, and the results of the simulations agree well with experimental observations. The data indicate that the specific interfacial free energy of a step edge on the (1 1 1) face of silicon in contact with its melt is about one-tenth of the specific interfacial free energy of the (1 1 1) facet.