MICROSTRUCTURES OF BIMETALLIC CLUSTERS - BOND ORDER METAL SIMULATOR FOR DISORDERED ALLOYS

Experimental bulk mixing data on disordered bimetallics of Ni, Cu, Ph, Pd, Ag, Ir, Pt, and Au are used to parametrize the recently developed bond order metal simulator (BOS-mixing) model, including a full error analysis. This model characterizes the variation of metal-metal bond strength with number and type of atomic neighbors. The model is shown to accurately ht experimental mixing energy curves as a function of co mposition irrespective of whether the curves are symmetric or asymmetr ic around the 50% value. As an illustration of the utility of the BOS- mixing model, we predict the microstructures of bimetallic clusters wi th 201 atoms (or 61% dispersion) and a composition of 50%-50%. The exa mples demonstrate how differences in surface energy, mixing energy, an d mixing entropy either compete or cooperate in determining the micros tructure of small bimetallic clusters. (C) 1997 Academic Press.