A comparative study of the molecules Cu2 and Ag2 by all electron ab initio HF–CI methods

In the present work the molecules Cu2 and Ag2 have been investigated using all electron ab initio Hartree–Fock (HF) and configuration interaction (CI) calculations. The basis sets used were of double zeta quality in general, but the 3d orbital for Cu and the 4d orbital for Ag were represented by triple zeta functions. The wave functions for the Cu2 and the Ag2 molecules have been analyzed in detail. Calculated spectroscopic constants have been derived and compared to experimental data, where available. Both for the Cu2 and the Ag2 molecules the calculated spectroscopic data vary considerably as the CI calculations exclude or include excitations from the valence d orbitals. The chemical bonds for both molecules are single bonds almost entirely due to sσg molecular orbitals.