Magic clusters MAu4 (M Ti and Zr) and their dimers:: How magic are they?

The stability of closed shell bimetallic magic clusters MAu4 (M = and Zr) investigated theoretically through ab initio molecular orbital calculations. Both these clusters have tetrahedral structures and are found to be associated with large values of the ionization potential, HOMO-LUMO gap as well as the binding energies, which are characteristic of the magic clusters. However, the cluster-cluster interaction energy corresponding to a dimer formation is found to be unusually high (similar to5-7 eV) in contradiction to the usual properties of a magic cluster and is attributed to a 3-center-2-electron M-Au-M type bridge bonding as well as aurophilic attraction. Gross geometrical features of the individual clusters are, however, mostly retained in the dimer, thus satisfying the basic requirements for the cluster-assembled materials. This work would have important implications in the design of novel cluster-based nanomaterials for various nanoscale applications. (C) 2004 American Institute of Physics.