The secondhyphen;order induction energy in the symmetryhyphen;adapted perturbation theory is expressed in terms of electron densities and polarization propagators at zero frequency of the isolated monomers. This expression is used to derive manyhyphen;body perturbation series with respect to the Moslash;llerndash;Plesset type correlation potentials of the monomers. Two expansions are introducedmdash;one based on the standard Moslash;llerndash;Plesset expansion of electron densities and polarization propagators, and the second accounting for the sohyphen;called response or orbital relaxation effects, i.e., for the perturbation induced modification of the monomerrsquo;s Fock operators. Explicit orbital formulas for the leading perturbation corrections that correctly account for the response effects are derived through the second order in the correlation potential. Numerical results are presented for several representative van der Waals complexesmdash;a rare gas atom and an ion Arndash;Na+, Arndash;Clminus;, and Hendash;Fminus;; a polar molecule and an ion H2Ondash;Na+and H2Ondash;Clminus;; two polar molecules (H2O)2; and a rare gas atom and a polar molecule Arndash;HCl and Hendash;HCl. It is shown that in the above systems, the significance of the correlation part of the induction energy varies from a very important one in the complexes of rare gas atoms and ions to a practically negligible one in the complexes of rare gases with polar molecules.
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