THEORETICAL CALCULATION OF VIBRATIONAL CIRCULAR-DICHROISM SPECTRA

We report calculations of the mid-IR unpolarized absorption and circul ar dichroism spectra of 4-methyl-2-oxetanone, 6,8-dioxabicyclo[3.2.1]o ctane and 1,7,7-trimethylbicyclo[2.2.1]heptan-2-one (camphor) based on harmonic force fields calculated using density functional theory (DFT ). A hybrid density functional, Becke3LYP, is used. The basis set is 6 -31G. The results are in impressive agreement with experimental spect ra. Calculations using the LSDA and BLYP functionals are much less suc cessful. Our results using Becke3LYP/DFT are compared with the predict ions of SCF and MP2 calculations. At the present time, the Becke3LYP/D FT methodology is clearly to be preferred in predicting mid-IR vibrati onal spectra.