A TIGHT-BINDING MOLECULAR-DYNAMICS SIMULATION OF THE MELTING AND SOLIDIFICATION OF SILICON

The melting of solid silicon and the cooling of liquid silicon are investigated using molecular dynamics. Both the Stillinger-Weber (SW) potential and the tight-binding bond model are used to calculate the forces. The electrical properties are investigated using an empirical pseudopotential method with a plane wave basis. The temperature at which the solid becomes unstable and passes to the liquid phase is found to be about 2300 K. The dependence of this temperature on cell size is investigated. On cooling, there are changes in some of the properties of the liquid: the energy per particle decreases, the diffusion constant decreases, and the low-frequency electrical conductivity decreases slightly as the temperature decreases. Between 1180 K and 980 K the liquid undergoes a transition to a glassy phase. There are large changes in the pair correlation function, the SW three-body energy distribution, the diffusion constant, the density of electron single-particle states and the electrical conductivity. All of these changes are consistent with increased tetrahedral bonding.