The frequency dependence of molecular polarizability is examined with the Tammndash;Dancoff approximation (TDA) and the random phase approximation (RPA) methods. Two computational algorithms for obtaining these values are discussed. The first uses diagonalization of the TDA state energy representation, which permits a rapid evaluation of several frequency points. The second involves matrix inversion, which has the advantage that the actual states need not be constructed, thus avoiding a large diagonalization. It is demonstrated that the inversion method may be performed with the atomic orbital (AO) twohyphen;electron integrals. This speeds the computation time for the static or dynamic polarizability in two ways. First there is a reduction in execution time due to circumventing the integral transform. Also when employing semiempirical methods, the I/O savings for retrieving the substantially shorter AO list further enhances performance. Test cases are evaluated using the intermediate neglect of differential overlap spectroscopic (INDO/S) wave function and include CH+, CO, and ferrocene. Results are compared against availableabinitiocalculations, followed by a discussion of the relative merit of the computational strategies.
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