ABINITIO SIMULATION OF BENZENE RAMAN INTENSITIES

C6H6 Raman scattering activities calculated from harmonic model ab initio Hartree-Fock 6-311++G(d,p) polarizability derivatives (and harmonic force fields calculated at the same level) accurately simulate experiment (to within 1% for the a1g modes). Accurate predictions are also made for the e2g modes (to within 5% for v7 and v9, and more poorly for v6 and v8 [in Fermi resonance with v6 + v1]) and for the e1g out-of-plane mode, v10. Only the v6 in-plane CCC bending mode scattering activity is found to be anomalous. Systematic variation of the basis set indicates that the benzene scattering activities and depolarization ratios are strongly dependent on inclusion of both carbon and hydrogen atom diffuse functions in the basis set. Predictions are also made for C-126D6 and for unmeasured intensities in C-136H6. Measurements of a1g mode scattering activities in the latter molecule are predicted to be useful in testing the harmonic Hartree-Fock Raman intensity model.