HyPol basis sets for high-level-correlated calculations of electric dipole hyperpolarizabilities

A series of the (second-order) polarized (HyPol) basis sets has been generated for the first- and second-row elements by extending the so-called polarized (Pol) basis sets proposed earlier. The new basis sets are to be used in calculations of the first and second hyperpolarizabilities. Their good performance has been verified in atomic and molecular calculations. The hyperpolarizabilities of HCN and HCP calculated with the HyPol sets are at least comparable in their accuracy with the best theoretical data obtained with considerably larger basis sets. The earlier Pol set, although inappropriate for calculations of atomic hyperpolarizabilities, performs quite well for molecules.