Molecular dynamics investigation of phase change induced by ultrafast laser irradiation

Irradiated by ultrafast laser pulse, the phase change phenomena in aluminum film are investigated via molecular dynamics simulation. The embedded-atom method potential is employed to describe atomic interactions. The laser heating is modeled by adding a kinetic energy term to the laser pulse irradiated atom at each time step. The resolidification is realized by thermal conduction to cool down locally melted atoms. The temporal and spatial distribution of atomic motion is recorded to compute the temperature evolution and structure change during melting and resolidification processes. The interface between solid and liquid is identified via Ackland analysis. Due to the temperature difference, diffraction profile of the resolidified aluminum is found different from the aluminum before laser irradiation. The simulation results provide helpful information on the atomic scale temperature variation and structure transformation underlying ultrafast laser induced phase change.