A DFT study of Hyper-Rayleigh Scattering (HRS) first hyperpolarizability of substituted polyene: Part (ii)

Several DFT functionals have been carried out to study the first hyperpolarizabilities βHRS of push-pull polyene as a function the basis sets, of electron  correlation, of the size, of the frequency dispersion and the geometry. These calculations confirm the huge effects of electron correlation, the Møller– Plesset (MP2) results reproduces the values of the first hyperpolarizability obtained with the reference CCSD(T) level. Among density functional theory  exchange- correlation functionals, B3LYP, M062X, B3P86 and CAM-B3LYP are comparable to the MP2 for characterizing the dynamic first  hyperpolarizability. The TDB3LYP/6-31+G* level show that, as increasing the the separation distance (dN···N /Å) and introducing a stronger donor the  avereage BLA value decreases and the βHRS increase. In addition, a quantitative relationship was established between the first hyperpolarizability HRS    and the separation distance (dN···N /Å) at MP2, B3LYP and M062X level of theory.