First-principles description for coherent phonon generation in diamond.

We report a first-principles description for coherent phonon generation in diamond based on the time-dependent density functional theory. The time-dependent Kohn-Sham equation is solved in real time in order to calculate the electron dynamics in periodic solid exposed to an ultrashort laser pulse. We find that the calculated forces acting on ions are consistent with measurements as regards the selection rule and the dependence on the laser intensity.