Mapping the global minima of binary Morse clusters: The effects of range mismatch

The putative global minima of binary Morse clusters have been systematically determined using the parallel basin-hopping method. Clusters A n A ( α ) B n B ( β ) with a total size nA + nB ranging between 5 and 55 atoms were studied for all (nA,nB) compositions, using a simple arithmetic combining rule for the range of the potential between unlike elements. Several order parameters are evaluated in order to characterize the global minima and to identify remarkable individuals. The stable structures generally show some phase separation with the long-range element surrounded by the short-range element, but some degree of mixing is found as well in order to minimize the overall strain. All clusters exhibit icosahedral features, except at the total size of 38, where depending on the range and composition truncated octahedra are found.