An ab initio study of vibrational corrections to the electrical properties of the second-row hydrides

Abstract

Accurate ab initio calculations of the dipole and quadrupole moments, polarizabilities and polarizability anisotropies are reported for the second-row hydrides, silane (SiH₄), phosphine (PH₃), hydrogen sulphide (H₂S) and hydrogen chloride (HCl). The Brueckner orbital variant of coupled cluster theory, namely Brueckner doubles (BD) with perturbatively linked triples (BD(T)) has been combined with large augmented triple-zeta basis sets to provide high-quality estimates that include vibrational averaging effects. Fourth-order energy and property derivatives have been calculated via a numerical least-squares procedure and used to calculate property zero-point vibrational corrections and pure vibrational polarizabilities from perturbation theory expressions. The effects of deuterium substitution on the properties is investigated and the frequency dependence of the polarizability and the polarizability anisotropy also studied. For those properties for which experimental data are available, a detailed comparison is made between theory and experiment. Vibrationally averaged BD(T) predictions of the dipole and quadrupole moments underestimate experiment by between 1 and 3% ; however, vibrationally averaged BD(T) mean polarizabilities typically lie within 0·5% of experiment. Calculated polarizability anisotropies are also shown to agree well with available experimental estimates, with the study demonstrating the importance of including vibrational corrections with accurate theoretical predictions of electrical properties.