A NONUNIQUE RELATIONSHIP BETWEEN POTENTIAL-ENERGY SURFACE-BARRIER AND DYNAMIC DIFFUSION BARRIER - FCC(111) METAL-SURFACE

作者：SANDERS DE; DEPRISTO AE

来源：Surface Science, 1992, 264(1-2): L169-L176.

DOI：10.1016/0039-6028(92)90149-Z

We present results from molecular dynamics simulations of the diffusion of a single metal atom on the surface of a fcc (111) metal. The central point that is addressed is the relationship between features of the potential energy surface and the diffusion rate when the surface (energy) corrugation is small. The systems considered here are Ag and Ag(111) and Rh on Rh(111). The interatomic forces were predicted using an approximation to the many-body non-self-consistent density functional based corrected effective medium theory (with acronym MD/MC-CEM), and an empirical Morse potential energy surface. Both potential energy forms are completely specified by the properties of the bulk systems, with the former also predicting very good values of surface energies on low Miller index surfaces and diffusion barriers on fcc (001) surfaces. Diffusion rates were extracted from the long time behavior of the adatom's mean square displacement and were found to obey an Arrhenius-type dependence on temperature. Good agreement with experimental diffusion rates was found with both potential energy surfaces. A different potential energy surface with much larger energy corrugation also yields agreement with experiment. We conclude that diffusion on these atomically smooth surfaces is governed by correlated dynamical behavior which eliminates the possibility of a unique extraction of the corrugation profile from experimental data.

• 出版日期1992-3-1