Numerical calculation of relaxation rates in amorphous silicon

Relaxation rates for strong and weak perturbations of the vibrational spectrum in amorphous silicon have been calculated using molecular dynamics simulations. A strong perturbation produced by creating a nonequilibrium normal mode distribution was found to relax on a 100 ps time scale. A weak perturbation generated by exciting a small number of modes in an equilibrated system yielded vibrational lifetimes on the order of 10 ps. Thermalization following the insertion of a heat pulse into the center of the simulation supercell also occurred on a 10 ps time scale.