THE CHEMICAL-BONDS IN CUH, CU-2, NIH, AND NI-2 STUDIED WITH MULTICONFIGURATIONAL 2ND-ORDER PERTURBATION-THEORY

The performance of multiconfigurational second order perturbation theo ry has been analyzed for the description of the bending in CuH, Cu-2, NiH, and Ni-2. Large basis sets based on atomic natural orbitals (ANOS ) were employed. The effects of enlarging the active space and includi ng the core-valence correlation contributions have also been analyzed. Spectroscopic constants have been computed for the corresponding grou nd state. The Ni-2 molecule has been found to have a 0(g)(+) ground st ate with a computed dissociation energy of 2.10 eV, exp. 2.09 eV, and a bond distance of 2.23 Angstrom. The dipole moments of NiH and CuH ar e computed to be 2.34 (exp. 2.4+/-0.1) and 2.66 D, respectively.