Dipole polarizability pseudospectra and C-6 dispersion coefficients for two-electron model systems

Convergence of dipole pseudospectra for the 2-electron model systems He and H-2 is studied for Riley-Dalgarno- and Kolos-Wolniewicz-type wavefunctions explicitly including electron correlation in terms of positive powers of t he interelectronic distance. 40-term pseudospectra for He and 34-term for H -2 give almost a 4-figure accuracy for the static polarizabilities of the m onomers and the resulting C-6 dispersion coefficients of the dimers. (C) 19 99 Elsevier Science B.V. All rights reserved.