Large scale random phase calculations for direct self-consistent field wavefunctions

We present an implementation of the double-direct random phase approximation (DDRPA) method for closed-shell and one-open-shell systems. The method is termed double-direct since (1) it is driven directly by the atomic orbital integrals, and since (2) it uses iterative techniques based on direct linear transformations for solving the RPA eigenvalue equations and sets of linear equations. The method can be used for calculating linear response properties such as polarizabilities and excitation spectra of large species. We demonstrate its potential by calculating excitation energies and transition moments as well as static and dynamic polarizabilities of para-nitroaniline. © 1993.