Analytic evaluation and basis set dependence of intensities of infrared spectra

摘要: Equations are presented for the analytic determination of dipole moment derivatives with respect to nuclear coordinates closed‐shell, open‐shell unrestricted, and restricted Hartree–Fock wave functions. The efficient evaluation these resulting infrared intensities simultaneously vibrational frequencies is discussed. Intensities a selection test molecules wide variety basis sets. It concluded that sets double‐zeta polarized or higher quality usually give correct qualitative information about ordering intensities, while smaller may not even predict most intense mode correctly. Quantitative accuracy using larger seems be limited primarily by use double harmonic approximation.