Ab initio 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 a_1g modes). Accurate predictions are also made for the e_2g modes (to within 5% for ν₇ and ν₉, and more poorly for ν₆ and ν₈ [in Fermi resonance with ν₆ + ν₁]) and for the e_1g out-of-plane mode, ν₁₀. Only the ν₆ 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 ¹²C₆D₆ and for unmeasured intensities in ¹³C₆H₆. Measurements of a_1g mode scattering activities in the latter molecule are predicted to be useful in testing the harmonic Hartree–Fock Raman intensity model.