Performance of DFT functionals for calculating the second-order nonlinear optical properties of dipolar merocyanines

The second-order nonlinear optical responses of a series of recently designed dipolar merocyanines are investigated using the 2006 Minnesota family of hybrid exchange-correlation functionals (XCFs), as well as the LC-BLYP, ωB97XD and CAM-B3LYP long-range (LR) corrected XCFs. The performance of these different levels of approximation is discussed in regard to reference second-order Møller-Plesset calculations and experimental data obtained from Hyper-Rayleigh Scattering (HRS) measurements. Particular focus is given to the influence of the amount of exact Hartree-Fock exchange included in the XCF on the magnitude of the static HRS responses, as well as to the impact of tuning the range-separation parameter in LR-XCFs, according to a system-specific nonempirical procedure. Frequency dispersion effects are also investigated, as well as their crucial role in the comparison between theoretical and experimental data. Evolution of the static HRS hyperpolarizability of a tricyanopropylidene-based merocyanine dye with the length of the polyenic bridge, as calculated using various ab initio and DFT approximations.