CALCULATION OF VIBRATIONAL LIFETIMES IN AMORPHOUS-SILICON USING MOLECULAR-DYNAMICS SIMULATIONS

The decay of normal-mode excitations is calculated for amorphous silic on through molecular-dynamics simulations within periodic supercells c onsisting of 216 and 4096 atoms. Phenomenological structural and inter atomic potential models are employed. At moderate temperatures, lifeti mes an found to be on the order of 10 ps and lifetimes of localized an d extended nonpropagating modes are comparable. These features are in agreement with related perturbation theory calculations, and in strong disagreement with the frustrated anharmonic decay predicted by the fr acton model and apparently with the results of anti-Stokes Raman exper iments performed at T=10 K. [S0163-1829(98)01319-8].