  We report results of molecular dynamics simulation of shock wave propagation
in silicon in [100], [110], and [111] directions obtained using a classical
environment-dependent interatomic potential (EDIP). Several regimes of
materials response are classified as a function of shock wave intensity using
the calculated shock Hugoniot. Shock wave structure in [100] and [111]
directions exhibit usual evolution as a function of piston velocity. At piston
velocities km/s the shock wave consists of a fast elastic precursor followed by
a slower plastic front. At larger piston velocities the single overdriven
plastic wave propagates through the crystal causing amorphitization of Si.
However, the [110] shock wave exhibits an anomalous materials response at
intermediate piston velocities around km/s which is characterized by the
absence of plastic deformations.
