AB-INITIO CALCULATION OF ATOMIC AXIAL TENSORS AND VIBRATIONAL-ROTATIONAL STRENGTHS USING DENSITY-FUNCTIONAL THEORY

We document a new density functional theory (DFT) methodology for the ab initio calculation of atomic axial tensors (AATs) using direct, ana lytical derivative methods and gauge-invariant atomic orbital (GIAO) b asis sets. AATs are calculated for ethylene oxide. Their accuracy is a ssessed using AAT sum rules and the experimental electric dipole momen t and paramagnetic susceptibility tensor. AATs calculated for the chir al molecule 6,8-dioxabicyclo[3.2.1]octane, in combination with DFT har monic force fields and atomic polar tensors, are used to predict vibra tional rotational strengths and vibrational circular dichroism (VCD) s pectra. Their accuracy is assessed by comparison with the experimental rotational strengths and VCD spectrum. The dependence of calculated r esults on density functional and basis set is explored. The DFT calcul ations are compared to SCF (Hartree-Fock) calculations carried out in parallel.