Jiahu Wang

Statistical electron correlation - coefficients and - holes in molecules*

SummaryElectron correlation in the H2, LiH and BH molecules has been analyzed in terms of the statistical correlation coefficients introduced by Kutzelnigg, Del Re, and Berthier. Angular, radial (in-out), longitudinal (left-right) and transverse correlation coefficients have been evaluated from both self-consistent-field (SCF) and configuration interaction (CI) wave functions. It has been found that these coefficients reflect fairly well the correlation behavior in the molecular system. The lack of spherical symmetry in molecular densities adds new features to these correlation coefficients and this information can be useful for the study of electronic structure in molecules. The correlation hole function, Fermi and Coulomb holes in these systems have also been calculated and discussed.

Ab initio study of the spin density of nitroxide radicals

Abstract The spin densities of the nitroxides H2NO, (CH3)HNO and (CH3)2 NO have been studied by iterative CI methods. Calculations at different geometries with various basis sets were performed. It is found that the spin distribution is delocalized within the N-O group, and substitution of the hydrogen atoms on the nitroxyl group by methyl groups changes the spin distribution significantly. Electron correlation, as well as the basis-set quality, plays an important role for the fluctuation of spin populations in the nitroxide radicals. It has been found that the spin density map can be predicted fairly well when correlation was included at certain levels and reasonable quality basis sets were employed. The spin polarization mechanism has been studied through a core excitation method. The superiority of local-spin-density (LSD) theory over the unrestricted Hartree-Fock (UHF) method in spin property studies is discussed.

Ab initio Study of the Electric Field Gradients in SCl2

Abstract The electric field gradients (EFG) in SCl2 have been computed with both self-consistent-field (SCF) and configuration-interaction (Cl) methods. The predicted EFG, along with the nuclear quadrupole moment QN of 35Cl and 37Cl from other sources, allows us to compare theoretical quadrupole coupling constants with new experimental results. The best values obtained agree with the experiment within 3%. It has been found that the principal axis of the coupling tensor does not coincide with the S-Cl internuclear axis, and the tilt angle has been predicted close to that from experiment.