Centrifugal distortions in molecules: An ab initio approach

Abstract

An ab initio approach to the theoretical description of centrifugal distortions in molecules is presented. The method is based on the calculation of the electronic energy changes and gradients accompanying rotationally induced distortions. A centrifugal distortion pathway in nuclear coordinate space is defined. Results are presented at the HF/6‐31G@B|@B| level for NH3, CH4, BF3, and SF6, and at the Guillemin–Zener level for H+2. Quartic centrifugal distortion parameters are computed for each molecule, with distortion anisotropies presented in the form of tensor coefficients. Centrifugally induced electric dipole moment coefficients are presented for CH4 and BF3 together with dipole moment changes for NH3. Agreement with experiment and with conventional theoretical descriptions is generally quite satisfactory, particularly for the tensor coefficients representing the cubic anisotropy in the distortions of the spherical tops CH4 and SF6.