The dipole moment derivatives of gaseous benzene: A comparison of experimental and ab initio values

The harmonic force constants, harmonic wavenumbers and dipole moment derivatives of benzene were calculated at the HF, MP2, MP3, CCD and CCSD levels of theory with several basis sets. It was determined that the signs of the dipole moment derivatives are consistent from all the methods. The MP2, MP3, CCD and CCSD calculations with the cc-pVDZ basis set all produce results that agree very well with the experimental values. It was determined that for benzene, the basis sets with diffuse functions over-estimate the dipole moment derivatives for the C-H stretch and out-of-plane HCCC bend, are not important for the in-plane HCC bend dipole moment derivatives and are essential for accurate determination of the C-C stretch derivatives.