Structural forms of model NinAlm, n+ m= 13, alloy clusters are studied for all stoichiometric
compositions using a many-body potential. These forms are distinguished by their
geometries (isomers) and the distributions of the two types of atoms within a given geometry
(homotops). General notions of mixing energy and mixing coefficient applicable to arbitrary,
including many-body, potentials are introduced. It is shown that for each stoichiometry the
energy ordering of the homotops, within classes defined by the isomeric form and the type of …