Electron count cluster-fusion rule

While the capping and fusion rules significantly increase the power of the PSEP model for clusters whose atoms have relatively high metal-metal connectivity, the newest extentions apply the model to lower connectivity clusters. For transition metals, 15n electrons (where n is the number of vertices) are expected for clusters whose metal atoms are connected to three other metal atoms (that is, three-connected clusters). " Examples include tetrahedra, cubes, and cuneanes. In the four-connected clusters, such as octahedra, square antiprisms, and cuboctahedra, the electron count can range from 14n to 14n -I- 4, depending on the nature of the polyhedron. ... 

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