A density functional theory study of the free radicals NH₂, NF₂, NCl₂, PH₂, PF₂, and PCl₂

Abstract

. Can. J. Chem. 72,695 (1994).The linear combination of Gaussian-type orbitals -density functional theory (LCGTO-Dm) 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.

The effects of nonlocal gradient corrections in density functional calculations of hydrocarbon radical hyperfine structures

“…This has also been found in previous studies [20,28,40]. The hydrogen isotropic hfs show a minor functional dependence, whereas for the carbon atoms, the variations in Aiso are substantial.…”

“…The discrepancy between theory and experiment can be related to the less accurate geometries (i.e., too short bond lengths and overestimated nonplanar geometries), obtained with the present choice of functional and basis set. Using geometries .in closer agreement with experiment, the calculated hfs are generally in excellent agreement with ESR and LMR data [ 19, 20,28,40].…”

“…Judging from the isotropic couplings, the two gradient-corrected functionals (BP and PWP) seem to generate a far better description of the core-region density. This effect has also been observed in previous studies of, e.g., H20+, OH, CN, Clz, NH2, NF?, and PH2 [20,40]. It has been shown that the nonlocal corrections give a buildup of unpaired spin-density at the coreand outer-valence regions of the heavy atoms relative to LDA and also generate a slightly lower spin density at the hydrogens.…”

Computational Study of the Mono- and Dianions of SO2, SO3, SO4, S2O3, S2O4, S2O6, and S2O8

“…Spin Densities and Predicted ESR Parameters. There is ample evidence that DFT can provide reliable spin densities for radical systems. − Since experimental ESR data is available for several sulfoxy radical anions, comparison with theoretical values may aid interpretation.…”

Theoretical Enthalpies of Formation of NHmCln: Neutral Molecules, Cations, and Anions

“…There have been several theoretical studies of NCl m compounds. − NCl 2 has been shown to have a 2 B 1 ground state, but there are four other states within 4 eV .…”