Accurate SCF Calculation for Ammonia and Its Inversion Motion

Abstract

A series of SCF calculations for the ammonia molecule in various gemoetries have been performed, using large basis sets of STO's. It is found that the height of the inversion barrier can be accurately predicted in the Hartree–Fock approximation, but that the basis set must be close to complete. Our largest calculations are in excellent agreement with previously reported calculations using Gaussian basis orbitals. A potential curve has been computed for the inversion motion using a near-Hartree–Fock basis set. The computed spectrum is in qualitative agreement with experiment; quantitative accuracy is not obtained, probably because the computed NH bond distance is too short.