Comparative DFT study of electronic structure and geometry of copper and silver clusters: Interaction with NO molecule

A comparative analysis of geometry and electronic characteristics, namely, vertical detachment energies (VDE) and excitation energies of neutral clusters with geometry of anions (Te) of anionic silver and copper clusters has been carried out within DFT model using a new functional developed recently [Vitaly E. Matulis, O.A. Ivashkevich, V. S. Gurin, J. Mol. Struct. (Theochem) 664–665 (2003) 291]. The obtained data show that the most stable anionic silver and copper clusters have very similar geometry. It has been shown, that properties defined by mainly s-electrons should be very similar for copper and silver clusters. However, the molecular orbitals with large contribution of d-atomic orbitals lie considerably closer in energy to the HOMO for copper clusters than for silver ones. Therefore, a substantial difference should be observed in such properties of silver and copper where d-electrons play an important role, for example, in their catalytic activity. The role of d-electrons along with VDE and ionization potential in catalytic activity is discussed in context of interaction of silver and copper tetramers with NO molecule. To study the influence of “ionic” versus “metallic” bonding on NO adsorption, the reactivity of Cu2Au2 cluster towards NO molecule has been studied and compared with the data obtained for Cu2Ag2 cluster.