Density functional study of structural and electronic properties of bimetallic copper-gold clusters: comparison with pure and doped gold clusters

The geometrical structures, relative stabilities, and electronic properties of small bare gold clusters Au-n(lambda) and bimetallic complexes of bare metal clusters with one copper atom Aun-1Cu lambda (charge lambda = 0, + 1, -1; 2 <= n <= 9) have been systematically investigated by means of first-principles density functional calculations at the B3LYP level. The results show that the most stable isomers have a planar structure and resemble pure gold clusters in shape, and no three-dimensional isomers were obtained for neutral and anionic doped gold clusters. However, the geometries of Aun-1Cu+ are found to undergo a structural change from two dimensional to three dimensional when the cluster contains 7 atoms. The calculated dissociation energy and second difference energy as a function of the cluster size exhibit a pronounced even-odd alternation phenomenon. Ionization potentials and electron detachment energies (both vertical and adiabatic) of Au-n(lambda) and Aun-1Cu lambda clusters are discussed and compared with available experimental results. A good agreement between experimental and theoretical results suggests good prediction of the lowest energy structures for all clusters calculated in the present study.