Anab initioSCF-LCAO-MO study of the phosphorus pyramidal inversion process in phosphine

Abstract

An extended ab initio SCF-LCAO-MO study of the PH₃ inversion process has been performed. Geometry optimization has been effected on both the pyramidal state and the planar form. The calculated molecular properties (geometry, dipole moment, ionization potentials, force constants) are in good agreement with experimental values. The barrier to inversion of PH₃ is calculated to be 36·7 kcal/mole, in good agreement with experimental data for substituted phosphines. The shortening of the P-H bond length in the planar form has a marked effect on the various energy terms. Polarization functions strongly influence the calculated molecular properties and the inversion barrier; their role is discussed. The physical origin of the PH₃ inversion barrier is studied and the process is compared to nitrogen inversion in NH₃.