Valence bond studies on NH₃ and PH₃

Abstract

Valence bond calculations are reported for the ground state of ammonia using a minimal Slater basis set and for the ground states of ammonia and phosphine using a contracted double-zeta basis set. In calculations with hybrid orbitals, the hybrid orbitals exhibit non-perfect following behaviour as the molecule bends. For ammonia, the most important structure is that in which the Natom carries a negative charge while for phosphine it is the covalent structure. Calculations using distorted two-centre hybrids show that the N-H bonds and P-H bonds are less ionic in the planar structure. For ammonia, the minimal basis set calculations give high values for the inversion barrier and the contracted double-zeta basis set calculations give low values. Values for the barrier in phosphine are comparable with other calculated values.