Studies in Configuration Interaction: The First-Row Diatomic Hydrides

Molecular properties of the first-row diatomic hydrides, calculated with accurate configuration-interaction wave functions, are presented. Ground-state functions, constructed from approximate natural orbitals, were determined at the equilibrium internuclear separation for each molecule. The basis sets used, were capable of reproducing recently published self-consistent-field energies to within 0.003 hartrees. A minimum of 70% of the correlation energy and an error in the dipole moment of less than 3% were obtained in a systematic study of each molecule. To attain this accuracy, large numbers of singly and doubly excited configurations were used in the wave functions.