We have developed atomic-scale material models capable of melting, crystallization and amorphization. These models feature molecular dynamics governed by Langevin equations of motion in which particle interact through attractive covalent forces and short-range repulsion forces. Also, we present an interactive virtual visualization tool for the simulation of atomic scale material behavior. An application of this research is to understand the processes that can control the quality of a single-crystal Si grown from the melt. 1