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

ABSTRACT

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 Au(n-1)Cu(lambda) (charge lambda = 0, +1, -1; 2 < or = n < or = 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 Au(n-1)Cu(+) 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 Au(n-1)Cu(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.