Molecular electric polarizabilities

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Abstract
The electric-field-variant (EFV) gaussian basis sets derived from the standard bases involving s and p-type GTO's are used for the calculation of the electric dipole polarizabilities of HF, H2O, NH3, and CH4. The explicit dependence of the basis functions upon the strength of the external electric field leads to a significant improvement of the computed polarizabilities in comparison with the results obtained from the corresponding field-independent bases. The accuracy of the computed polarizabilities and polarizability anisotropies is comparable to that achieved in the best, near-Hartree-Fock perturbation calculations employing much larger polarized basis sets. Using the EFV GTO's leads to a simultaneous improvement of the dipole moments of polar molecules. The calculated dipole moments become also close to the corresponding Hartree-Fock values. The basis set requirements for the EFV GTO approach are analysed. It is concluded that the initial field-independent basis set has to involve valence-shell orbitals with rather low orbital exponents. The use of the polarization functions does not appear to be necessary for the present method. The dipole moment and polarizability values are also almost independent on the contractions of the set of primitive Gaussians. Some rules for a priori choice of the so-called scale parameter which enters the EFV GTO's and in principle has to be optimized are discussed.