Electromigration was studied in a driven diffusive lattice gas whose continuous Monte Carlo dynamics generated a higher particle mobility in areas with lower particle density. At low vacancy concentrations and temperatures, the vacancy domains tended to be faceted. The external driving force caused large domains to move much more quickly than small ones; thus producing exponential domain growth. At higher vacancy concentrations and temperatures, even small domains had rough boundaries. The velocity differences between domains were then smaller, and relatively short simulation times produced an average domain length scale which approximately obeyed an expression of the form, L = AtB, where B varied from about 0.55 at 50% filling to about 0.75 at 70% filling. This growth was faster than the t1/3 behavior of the usual conserved order-parameter Ising model. A simple scaling picture, which neglected velocity fluctuations but included the cluster-size dependence of the velocity, predicted growth according to t½. The conclusion that small driving forces could significantly enhance coarsening was suggested to be relevant to Cu3Ba2YO7 electromigration experiments.

L.K.Wickham, J.P.Sethna: Physical Review B, 1995, 51[21], 15017-26