Analytical calculation of full configuration interaction response properties: Application to be

The computation of the frequency dependent linear and quadratic response functions is formulated at the full configuration interaction (FCI) level of theory. It is demonstrated that the frequency dependent polarizability (for real and imaginary frequencies) may be obtained with quadratic dependence on the error in the solution of the response equations. An efficient solution of the FCI response equations for large imaginary frequencies is developed. Initial application is to the Be atom in the standard 9s9p5d basis. Reported results include transition energies and dipole moments for the first few singlet and triplet S, P, and D states, the first polarizability at real and imaginary frequencies, the C₆ coefficient, and the static second hyperpolarizability. Comparison to prior theoretical results in this basis, and to experiment, is made where possible. It is the first time that many of these properties have been computed at the FCI level of theory for any system.