Showing papers on "Full configuration interaction published in 1971"

Electronic Structures and Potential Energy Curves for the Low‐Lying States of the CN Radical

Abstract: At 11 internuclear separations ab initio calculations have been carried out on those 59 molecular states of CN which dissociate to atomic limits up to 1DC + 2DN. Four electrons are held frozen in carbon and nitrogen 1s Hartree–Fock atomic orbitals, and a full configuration interaction is carried out for the remaining nine electrons using optimized 2s and 2p Slater‐type orbitals on each atom. The 2Π calculations, which include 486 configurations, are the most complicated. Eighteen significantly bound states (De ≥ 0.84 eV) were obtained, nine of which have been observed spectroscopically. With the exception of the third 2Π state, the theoretical ordering of states agrees with experiment. Three of the states never observed experimentally (4Σ+, 4Π and 4Δ) lie below all but three of the known states of CN. Calculated spectroscopic constants are compared with experiment. The potential curves show many interesting features, including potential maxima in the 4Σ−, 2Σ−, J 2Δ, and 2Π IV bound states. By performing n...

Configuration interaction in rare earth ions. II. Magnetic interactions

Abstract: For pt. I see abstr. A25410 of 1971. The usefulness of a 'model building' approach to rare earth configuration interaction is emphasized as an alternative to doing full ab initio calculations. Second order perturbation theory is used to calculate the eleven parameters which characterize the effective two-electron magnetic interaction in both Pr2+ and Pr3+. Good agreement is obtained with the Pr2+ experimental parameters without introducing screening.

Configuration‐Interaction Calculations for Small Pi Systems. IV. Spin and Charge Densities of Various Heteromolecules

Abstract: The spin and charge densities of a number of substituted benzene heteromolecules are calculated by full configuration interaction. The results are compared with those calculated by Huckel theory and are found to be qualitatively in agreement. The significance of the near degeneracy of the Huckel molecular orbitals is discussed. Two types of substituted benzenes are considered, the electropositive aza substitution and the electronegative methyl substitution. Particular consideration is given to the positive and negative ions.