Memory effects in the frictional damping of diffusive and vibrational motion of adatoms

Abstract

We investigate the memory effects in the frictional damping of the vibrational and diffusive motion of an adatom. Using the molecular-dynamics simulation method, we solve the equations of motion of an adatom in a periodic potential coupled to substrate phonons which are in turn coupled to a heat bath. The frustrated translational mode and the diffusion constant of the adatom is studied by calculating appropriate time-dependent correlation functions. We discuss our numerical results in the context of a generalized Langevin equation. The validity of analytic approximations to the memory function in the Langevin equation such as mode-mode coupling and initial value approximation are examined by comparing the analytic results with those obtained from the numerical simulations. © 1996 The American Physical Society.