CORRECTION VECTOR METHOD FOR EXACT DYNAMIC NLO COEFFICIENTS IN RESTRICTED CONFIGURATION-SPACE

The correction vector technique for obtaining dynamic nonlinear optica l (NLO) coefficients is extended to semi-empirical CI schemes; The tec hnique is established by comparison with full sums over states (SOS) c omputations on a small system. Comparison of the results of a truncate d SOS method and the full-space NLO coefficients from the correction v ector method in a CI space of 1347 configurations shows that the SOS t echnique with 50 excited states for para-nitroaniline gives reliable a lpha and beta values, but the gamma value is off by more than a factor of 2 for the dominant components. The correction vector technique, be sides being exact in the chosen Ct space, is also computationally more efficient than the truncated SOS technique.