The inversion potential for NH3 using a DFT approach

Using a density functional theory approach, we generate a potential energy surface (PES) and, by a least-squares method, we obtain a polynomial function which represents the unidimensional potential along the inversion coordinate, with a very high precision. The inversion spectrum of NH3 is then determined by solving the Schrödinger equation for this potential, using a better approximated reduced mass which is a function of the inversion coordinate. The calculated inversion frequencies obtained through this method are compared against those generated by Hartree–Fock theory and also with the experimental values. We find that our theoretical results are by far the most accurate.