Coriolis couplings in variational computations of vibrational spectra beyond the harmonic approximation: implementation and validation

Coriolis couplings have been added to perturbative and variational implementations of anharmonic computations of vibrational spectra. The results for several medium size molecules show that Coriolis couplings cannot be neglected for quantitative studies, since they can account in some cases for more than 20% of the overall anharmonic correction. The effect is particularly important for fundamental vibrations involving out of plane motions and for combination bands involving stretchings and out-of-plane bendings. In all cases perturbative inclusion of these terms leads to results very close to their variational counterparts. This is particularly significant for an effective perturbative-variational approach to the anharmonic spectra of large molecules.