Ab initio molecular dynamics simulation of laser melting of graphite

The method of ab initio molecular dynamics, based on finite temperature density functional theory, is used to simulate laser heating of graphite. We find that a sufficiently high concentration of excited electrons dramatically weakens the covalent bond. As a result the system undergoes an ultrafast melting transition to a metallic state. This process appears to be similar to, although considerably faster than, laser melting of silicon. The properties of the laser-induced liquid phase of carbon are found to depend crucially on the level of electronic excitation. All these features are in qualitative agreement with the experimental behavior. (C) 1998 American Institute of Physics.