ABINITIO CALCULATION OF VIBRATIONAL CIRCULAR-DICHROISM SPECTRA USING ACCURATE POST-SELF-CONSISTENT-FIELD FORCE-FIELDS - TRANS-2,3-DIDEUTERIOOXIRANE

The ab initio calculation of harmonic force fields using post-self-con sistent-field (post-SCF) methods has recently increased greatly in eff iciency. As a result, accurate post-SCF harmonic force fields are now achievable for experimentally accessible chiral molecules. This in tur n permits for the first time comparison to experiment of ab initio pre dictions of vibrational circular dichroism (VCD) spectra based on accu rate harmonic force fields. This advance is exploited here in the calc ulation of the VCD spectrum of trans-2,3-dideuteriooxirane using a lar ge basis set MP2 force field. Excellent accord with recent experimenta l work is achieved. With the exception of C-H and C-D stretching modes , residual differences between predicted and experimental VCD intensit ies can be attributed to the incomplete inclusion of correlation in th e calculation of atomic axial tensors.