CONVERGENCE OF SURFACE-DIFFUSION PARAMETERS WITH MODEL CRYSTAL SIZE

A study of the variation in the calculated quantities for adatom diffu sion with respect to the size of the model crystal is presented. The r eported quantities include surface diffusion barrier heights, pre-expo nential factors, and dynamical correction factors. Embedded atom metho d (EAM) potentials were used throughout this effort. Both the layer si ze and the depth of the crystal were found to influence the values of the Arrhenius factors significantly. In particular, exchange type mech anisms required a significantly larger model than standard hopping mec hanisms to determine adatom diffusion barriers of equivalent accuracy. The dynamical events that govern the corrections to transition state theory (TST) did not appear to be as sensitive to crystal depth. Suita ble criteria for the convergence of the diffusion parameters with rega rd to the rate properties are illustrated.