Ab initio studies on the structures and vertical electron detachment energies of copper-water negative ion clusters Cu−(H2O)n and CuOH−(H2O)n−1

The equilibrium geometries of Cu−(H2O)n and CuOH−(H2O)n−1 (n=1 and 2) negative ion clusters have been optimized by performing ab initio calculations at the second-order Møller-Plesset (MP2) approximation with extended basis sets. For comparison, the geometries of X−(H2O)n (X=F, Cl, Br and I) are optimized at the same level of approximation. The calculated results show that all hydrogen atoms in the equilibrium geometries of Cu−(H2O)n (n=1 and 2) are equivalent to each other, which is contrasted to the geometries of X−(H2O)n, where one of the hydrogens of H2O is more strongly bonded to X−. The calculated vertical electron detachment energies as well as hydration energies with MP4SDTQ are very close to the corresponding experimental data.