Surface effective-pair interactions in a model transition-metal alloy

For a model transition-metal alloy, we find that changes in the third and fourth moments of the electronic density of states alter the effective-pair interaction (EPI) ordering range. The EPI dependence on concentration, single-site energy, and crystal face is explained by showing the dependence of the state-density third and fourth moments on these variables. Examples illustrating these effects are given for bcc and fcc surface EPI's. From this analysis, we find that bulk-clustering and surface-ordering behavior is more likely than bulk-ordering and surface-clustering behavior. In addition, we find that the presence of broken bonds tends to increase the ordering range.