A DENSITY-FUNCTIONAL THEORY STUDY OF THE FREE-RADICALS NH2, NF2, NCL2, PH2, PF2, AND PCL2

The linear combination of Gaussian-type orbitals - density functional theory (LCGTO-DFT) approach is used to study geometries and hyperfine structures of a set of neutral radicals. Each of the title molecules is investigated by means of local density approximation calculations, and using the Becke-Perdew and Perdew-Wang-Perdew corrections to the exchange and correlation functionals. The effects of local vs. non-local potentials and of various basis sets are investigated. Total densities and unpaired spin densities are compared. The isotropic couplings are found to be very dependent on the type of exchange functional used, whereas the anisotropic couplings are relatively insensitive to the choice of basis set and functional. in most cases, the Perdew-Wang exchange corrections provide isotropic couplings in satisfactory agreement with experiment.