Frequency and Solvent Dependence of Nonlinear Optical Properties of Molecules

Abstract

Real-time, time-dependent density functional theory (RT-TDDFT) is used for the evaluation of the frequency dependence of the polarizability and hyperpolarizability of molecules intended for application in electrooptic devices. These first-principles computational methods are powerful but costly. Significantly easier calculations based on a simplified version of second-order time-dependent perturbation theory, the "two-state model" (TSM), are here used to provide another estimate of the frequency dependence. Furthermore, the TSM calculations can be done in the presence of a dielectric reaction field (the polarizable continuum model method) to provide estimates of the solvent dependent properties in addition to the frequency-dependent properties. Here we use RT-TDDFT to assess the accuracy of the frequency dependence of the TS, and a ground-state finite field calculation to assess the effect of additional states on the static hyperpolarizability. Both frequency and dielectric responses are important for evaluation of the suitability of molecules in nonlinear optical applications. † Part of the "Larry Dalton Festschrift".

Two-electron Rabi oscillations in real-time time-dependent density-functional theory

“…28 In contrast to the linear response matrix formulation of TDDFT, real-time (RT) TDDFT propagates the electron density in the time-domain, including the response of the density to all orders, well beyond the perturbative regime. [29][30][31][32][33] Because of this time-resolved nonlinear treatment, RT-TDDFT can provide substantially more information about the electron dynamics of the system, including rates of electron transfer, charge-transfer pathways, 34 frequency-dependent nonlinear field effects, 35 and possible routes to double excitations missing from linear response theory. 36 One area of research that RT-TDDFT appears to have large potential for providing theoretical insight, particularly when combined with nonadiabatic Ehrenfest dynamics, is strong-field interactions and comparison to experimental ultrafast laser controlled electron dynamics for multi-electron systems.…”

Theory-Guided Design of Organic Electro-Optic Materials and Devices

“…Quantum and statistical mechanics have played a critical role in the engineering of simple molecular materials; however, the complexity of OEO materials poses a challenge for use of such methods. Recently, the utility of computation of linear and nonlinear optical properties of OEO materials including the dependence of properties on dielectric permittivity [53,54] and optical frequency [55][56][57] by time-dependent density functional theory, TD-DFT (including real-time time-dependent density functional theory, RT-TD-DFT [55][56][57]) has been advanced. Improvements have been based on careful correlation of theoretical and experimental data and on the development of new hybrid functionals (e.g., M06-2X gives better reproduction of trends in OEO materials going from heteroaromatic bridges, e.g., YLD156, to polyene bridges, e.g., YLD124, compared to the highly utilized B3LYP functional).…”

N‐Ethyl Carbazole Derived D‐π‐A‐π‐D Based Fluorophores: Consolidated Spectroscopic, Viscosity and DFT Studies

“…[60][61][62][63] Computations are a convincing tool to examine the geometrical and electron properties of the chromophores. [64][65][66] Density functional theory (DFT) based computations give insights into the functional properties like hyperpolarizability at the molecular level with well-defined electron correlation energies and are cost effective. [67,68] NLOphoric materials were restricted to one-dimensional (1D) systems with D and A moieties linked by π-conjugated bridges (D-π-A).…”

“…Computations are a convincing tool to examine the geometrical and electron properties of the chromophores . Density functional theory (DFT) based computations give insights into the functional properties like hyperpolarizability at the molecular level with well‐defined electron correlation energies and are cost effective .…”