Laser thermal annealing of pre-amorphized silicon can be used to achieve sharp junctions with enhanced dopant activation. The changes in the properties of silicon as a consequence of the phase transition form amorphous to liquid caused by the laser annealing could influence the subsequent recrystallization and the activation of the dopants. In this work we have used the molecular dynamics simulation technique to study the physics of the amorphous-to-liquid transition in silicon. The changes in density, internal energy, structure and diffusion behavior are obtained from the simulations and analyzed. We have observed that for temperatures between the amorphous and crystal melting points there exists an intermediate phase which shares some of the properties of the amorphous and liquid silicon.