Assessment of DFT Exchange-Correlation Functionals for Evaluating the Multipolar Contributions to the Quadratic Nonlinear Optical Responses of Small Reference Molecules.

The hyper-Rayleigh scattering responses as well as the multipolar contributions to the first hyperpolarizabilities are calculated by means of density functional theory for a series of reference molecules (acetonitrile, dichloromethane, trichloroacetonitrile, chloroform, carbon tetrachloride), covering the whole range of dipolar/octupolar character. The performance of various exchange-correlation functionals is addressed by comparison to CCSD(T) calculations. The best functionals turn out to be LC-BLYP, M05-2X, and M06-2X.