The nonempirical calculation of second-order molecular properties by means of effective states. III. Correlated dynamic polarizabilities and dispersion coefficients for He, Ne, H2, N2, and O2

Abstract

Intramolecular correlation contributions to long-range dispersion interactions between closed shell and open shell molecules have been studied by means of perturbation calculations in bases of configuration state functions. All necessary dynamic polarizabilities have been calculated in large bases for He, Ne, H2, N2, and O2. These calculations employ a modified version of an algorithm which was published recently. Basis sets consisting of single and double substitutions from the reference function have been employed. It is shown that in a basis of unperturbed SCF-MO’s the truncation of the configuration basis at the single and double CI level does not give a satisfactory description of the correlation effects. The inclusion of triply excited states is studied for the Ne atom. This improves the results considerably. The possible extension of the present approach to larger systems is discussed.