Analytic calculations of nonlinear mixed electric and magnetic frequency-dependent molecular properties using London atomic orbitals: Buckingham birefringence

We present the results of the first gauge-origin independent calculations, carried out at Hartree–Fock level, of the molecular parameters that describe the electric-field-induced linear birefringence, also known as Buckingham birefringence. Focus is in particular on the temperature-independent contribution to the observable. We employ a recently developed analytical scheme for calculating frequency-dependent molecular properties of arbitrary order for self-consistent field methods using basis sets that depend explicitly on the frequency and on the external perturbations. The method is applied to naphthalene, fluorobenzene and furan, three systems for which the Buckingham birefringence has been studied experimentally. It is demonstrated that LAOs lead to significant improvements in the basis set convergence of the temperature-independent contribution to the Buckingham birefringence, and that the results obtained on the basis of aug-cc-pVDZ quality and London atomic orbitals are closer to the basis set limit than the results obtained on the basis of conventional aug-cc-pVQZ quality. The computed values can be used to correct for the neglect of the temperature-independent higher order contribution often implied in the derivation of the effective quadrupole moments from experimental measurements of the induced birefringence at a single temperature.