Pseudopotential MRD CI calculations of nickel-containing molecules. II. The electronic 1Σ + ground state and 20 low-lying excited states of the NiSi molecule

Abstract

Using the MRD CI procedure within the pseudopotential approximation the potential energy curves of the 1Σ + ground electronic state and of twenty low-lying excited states of the NiSi molecule are calculated. The chemical binding of the molecule in its ground state is effected by a σ bond originating from a coupling between Ni 4sσ and Si 3pσ orbitals and by a partially occupied π bond between Ni 3dπ and Si 3pπ orbitals. The dissociation energy amounts to 1.89 eV which is 58% of the experimental value. Equilibrium distance, vibrational frequency and dipole moment, experimentally not known, are predicted theoretically to be 4.23 au, 303 cm −1, and 0.677 D, respectively. Several methodical aspects, including a possible bias of CI wavefunctions to the SCF HF orbitals, the choice of the configurational spaces, and the corrections of basis set superposition and size-consistency errors are discussed.