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Density functional theory schemes based on conventional exchange-correlation functionals have been used to establish dipole moment, polarizability, and first and second hyperpolarizabilities of push-pull pi-conjugated systems. It is concluded that current exchange-correlation functionals do not accurately describe the polarization of conjugated systems when the polarization is the result of donor/acceptor substitution or an external field or both.

The electronic excitations and frequency-dependent electronic second hyperpolarizability gamma (-omega; omega, omega, -omega)) of the five-ring heterocycles furan, thiophene, selenophene, and tellurophene have been reinvestigated using time-dependent density functional theory. Increased hyperpolarization for molecular dimer species suggests that intermolecular interactions may provide a simple explanation for the large deviations between recent ab initio calculations and experimental condensed-phase data.