CAUCHY MOMENTS AND DISPERSION COEFFICIENTS USING COUPLED-CLUSTER LINEAR-RESPONSE THEORY

Expressions for the even Cauchy moments for nonvariational methods hav e been derived using the time-averaged quasienergy Lagrangian techniqu e. The expressions obtained require the solution of linear equations b ut do not involve a sum over individual excited-state contributions. A n implementation is reported for the coupled cluster models CCS, CC2, and CCSD and calculations have been performed for the Cauchy moments a nd the Verdet and Cotton-Mouton constants of the Ne atom and for the C -6 dispersion coefficient of the Ne-2 dimer. (C) 1997 American Institu te of Physics.