Theoretical studies of the surface phonon linewidth

A brief review of two theoretical methods for calculating the linewidth of surface phonons is presented with specific application to the low-Miller-index surfaces of Ag, Cu, and Al. In the quasi-analytic method, linewidths are calculated by treating the cubic term of a reliable interatomic potential in first-order, time-dependent perturbation theory. In molecular dynamics (MD) simulations, linewidths are obtained from appropriate correlation functions and include the fully anharmonic contribution of the interaction potential. Surface relaxations and phonon frequencies calculated in the harmonic approximation, using selected many-body interatomic potentials, are found to be in good agreement with results from experimental data and ab initio calculations. At 300 K, the surface phonon linewidths range approximately between 1 and 0.1 THz, and are found to be in reasonable agreement with the values deduced from experiments. Some disagreement is found between results from perturbative methods and M simulations. For the low-Miller-index surfaces of Ni, available results from MD simulations also summarized.