Abstract: MP2 method and different functionals such as M06-HF, M06-2X, CAM-B3LYP, PBE0, B3LYP and M06L incorporating different XC amounts were used to calculate the static first hyperpolarizabilies β(0) of eight molecules which are derivatives of benzene, stilbene and diphenylacetylene. The values were then compared to the experimental ones. The M06-2X functional was then selected for further calculations. NBO calculations were also performed to define the intramolecular charge transfer in each molecule. TD-DFT calculations were performed taking into account the solvent effect using the IEF-PCM formalism. Some parameters characterizing the vertical transitions such as the wavelength of the maximum absorption λ_max were compared to the experimental ones. Finally, solvation Gibbs free enthalpy ΔG_solv values have also been examined in order to determine which the specific solvent for a given molecule is.

Key words: First hyperpolarizability, DFT, TD-DFT, Push-pull molecules, NBO, Charge transfer