Dispersion coefficients and frequency-dependent polarizabilities

Extensions of previous methods for obtaining two‐ and three‐body dispersion coefficients are presented. Many‐dimensional arrays in inner projections are utilized. The required matrix elements are expressed in terms of atomic frequency (Cauchy) moments. Approximate dynamic polarizabilities are derived using generalized inner projections, and a number of theorems for definite operators are extended to more general cases. Numerical results for both two‐ and three‐body dispersion coefficients are reported.