THEORY OF SURFACE-DIFFUSION - CROSSOVER FROM CLASSICAL TO QUANTUM REGIME

A theory is developed for adatom diffusion on surfaces, employing the memory function formalism. The diffusion constant is expressed in terms of static correlation functions which are computed via Monte Carlo path integrations. Our theory is valid at all temperatures in the high friction limit and indicates a sharp crossover from the classical Arrhenius regime at high temperatures to the quantum tunneling regime at low temperatures. Comparisons with experimental data are presented for the H/Ni(100) system.