On the molecular electric quadrupole moment and the electric-field-gradient-induced birefringence of CO2 and CS2

An ab initio investigation of the quadrupole moment, the polarizability anisotropy and the temperature-independent term entering the electric-field-gradient-induced birefringence (EFGB) of CO2 and CS2 is presented. For the latter property, the results allow us to analyze numerically the differences between two semiclassical theories of the EFGB for nonpolar systems. Accurate electric quadrupole moments are obtained from the combined use of coupled cluster methods and diffusely augmented correlation-consistent basis sets. For CO2, our best ab initio estimate of Θ0=(−14.29±0.09)×10−40 Cm2 is in excellent agreement with the two most recent experimentally deduced results (−14.3±0.6)×10−40 Cm2 and (−14.27±0.61)×10−40 Cm2.