Monte Carlo simulations of void-nucleated melting of silicon via modification in the Tersoff potential parameters

Molecular dynamics simulations of silicon melting reported in the literature using Tersoff's potential give melting temperatures about 50% higher than the experimental value. To address this discrepancy, we have proposed a modification to the values of the parameters of the Tersoff potential. This modification involves a change in the magnitude of 3 of the 12 parameters in the Tersoff potential as an effective means for bringing down the melting point close to the experimental value. The melting point is determined by performing Monte Carlo simulations using the empirical void-nucleated melting procedure. In addition to an agreement of the computed melting point with the experiment, the modified parameters also bring the density of the liquid and the solid at the melting point into good agreement with the experiment without significantly altering the density and energy values of the solid crystal at room temperature. The coordination number and specific heat of the liquid are also found to be in better agreement with the experiment when the modified set of parameters is used. A comparison of density over a wide range of temperatures shows that the density of the solid predicted by the Tersoff potential with the modified parameters is larger than that given by the unmodified parameters. This difference, however, is not appreciable at room temperature; it increases with temperature and is about 1% at the melting point. The computed cohesive energy of the solid, the point defect energy corresponding to a vacancy, and the surface energy values for (100) and (111) surfaces are also found to be nearly the same for the modified as well as the unmodified parameters.