ANHARMONIC CORRECTIONS TO VIBRATIONAL ENERGIES OF MOLECULES - WATER AND DIDEUTERIOOXIRANE

Anharmonic contributions to vibrational energies and absorption and vi brational circular dichroism spectral intensities are discussed for th e example of trans-2,3-dideuteriooxirane. Higher energy and dipole der ivatives are calculated ah initio at the Hartree-Fock level in Cartesi an coordinates. The combination of variational and perturbational calc ulations of vibrational energies allows consistent treatment also for the case of Fermi resonances. A cubic energy term can account for the main part of the anharmonic contribution.