The melting lines of model silicon calculated from coexisting solid–liquid phases

The molecular-dynamics simulation approach [Morris and Song, J. Chem. Phys. 116, 9352 (2002)] is employed to calculate the melting lines for two model systems of silicon: the Stillinger–Weber (SW) model and the Tersoff-89 model. To address the anisotropic stress problem indicated in the previous paper, a slightly improved simulation procedure is used to prepare the coexisting solid and liquid phases at the thermodynamic equilibrium. For the SW silicon, the calculated melting temperature Tm at zero pressure agrees with that based on the free-energy calculation [Broughton and Li, Phys. Rev. B 35, 9120 (1987)]. The dependence of Tm at zero pressure on the selected solid surface orientation is also examined. The relative difference between Tm calculated based on the sharp Si (111)/liquid interface and the faceted Si (100)/liquid interface is less than 1%. Both models predict that the melting line exhibits a negative slope, which is consistent with the fact that the molar volume of the solid is larger than that of liquid upon melting.