Dipole polarizability and second hyperpolarizability of difluoroacetylene: Basis set dependence and electron correlation effects

Ab initio calculations of the static dipole polarizability and the static and dynamic second hyperpolarizabilities, including the electron correlation effects via the standard Coupled Cluster method with single and double excitations (CCSD) and non-iterative triple excitations (CCSD(T)) as well as the vibrational motion (nuclear relaxation) effects by means of the Finite Field method formulated by Kirtman and co-workers, have been carried out for difluoroacetylene (C₂F₂). The basis set dependence of the geometry parameters and molecular properties using various types of basis sets (ANO-L, POL, HyPOL, aug-cc-pVTZ) is analysed. A particular attention is devoted to the evaluation of the electron correlation effects on the vibrational contributions to the molecular properties.