TY - JOUR
T1 - Ab initio investigation of geometry changes during inversion of NH 3, NH2F, NH2, NF3 and PH 3, PH2F, PHF2, PF3
AU - Schmiedekamp, Ann
AU - Skaarup, Steen
AU - Pulay, Péter
AU - Boggs, James E.
PY - 1977
Y1 - 1977
N2 - Ab initio SCF molecular orbital calculations with complete geometry optimization have been performed using consistent basis sets for each member of the series NH3, NH2F, NH2, NF3 and PH3, PH2F, PHF2, PF3. The calculations were repeated using the same basis sets with the molecules constrained to the planar configuration which is the transition state for inversion, all other geometrical parameters being energy optimized. In the planar configuration, shorter N-F, N-H, and P-H bonds resulted as well as a change from the nearly equal pyramidal bond angles to highly asymmetric planar bond angles with ∠HXH> ∠HXF> ∠FXF. Omission of polarization functions from the basis set produced longer P-F and N-F bonds. Regardless of the inclusion or exclusion of d atomic Orbitals in the basis set, substitution of fluorine for hydrogen yields regular increases in inversion barrier heights. Exclusion of d atomic orbitals results in inversion barriers that are smaller by nearly the same amount for all molecules in a series. The increase in barrier with substitution of fluorine for hydrogen is correlated with an increase of s character in the lone pair. Dipole moment and components, bond moments, and lone pair moments are discussed. Effects of varying the d orbital exponent coefficient on the central atom were examined.
AB - Ab initio SCF molecular orbital calculations with complete geometry optimization have been performed using consistent basis sets for each member of the series NH3, NH2F, NH2, NF3 and PH3, PH2F, PHF2, PF3. The calculations were repeated using the same basis sets with the molecules constrained to the planar configuration which is the transition state for inversion, all other geometrical parameters being energy optimized. In the planar configuration, shorter N-F, N-H, and P-H bonds resulted as well as a change from the nearly equal pyramidal bond angles to highly asymmetric planar bond angles with ∠HXH> ∠HXF> ∠FXF. Omission of polarization functions from the basis set produced longer P-F and N-F bonds. Regardless of the inclusion or exclusion of d atomic Orbitals in the basis set, substitution of fluorine for hydrogen yields regular increases in inversion barrier heights. Exclusion of d atomic orbitals results in inversion barriers that are smaller by nearly the same amount for all molecules in a series. The increase in barrier with substitution of fluorine for hydrogen is correlated with an increase of s character in the lone pair. Dipole moment and components, bond moments, and lone pair moments are discussed. Effects of varying the d orbital exponent coefficient on the central atom were examined.
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U2 - 10.1063/1.433852
DO - 10.1063/1.433852
M3 - Article
AN - SCOPUS:0006449366
SN - 0021-9606
VL - 66
SP - 5769
EP - 5776
JO - The Journal of chemical physics
JF - The Journal of chemical physics
IS - 12
ER -