Basis set convergence and correlation effects in vibrational circular dichroism calculations using London atomic orbitals

Abstract

Using London atomic orbitals (LAO) the vibrational dipole and rotatory strengths are derived for the natural connection of molecular orbitals. The resulting expressions are significantly simpler than the previous ones obtained for the symmetric connections. Single configurational self-consistent field (SCF) calculations of vibrational dipole strengths and LAO vibrational rotatory strengths are carried out for five small and medium sized chiral molecules using various basis sets. These calculations show similar basis set convergence for the vibrational dipole strengths and the vibrational rotatory strengths. The vibrational rotatory strengths for trans[2,3-²H₂]oxirane from a multiconfigurational (MC)-SCF wavefunction expanded in 30039 determinants give an improved agreement with the experimental spectrum compared with the rotatory strengths from the SCF wavefunction. The agreement of the MCSCF spectrum is comparable to those of previous MP2 spectra.