The Choice of Appropriate Density Functional for the Calculation of Static First Hyperpolarizability of Azochromophores and Stacking Dimers

摘要

The effect of the stacked azo-chromophore dimer formation on the values of static first hyperpolarizability is studied in the framework of the DFT-based approach; calculations were also performed at the MP2 level. A number of dispersion-corrected density functionals-B97D, omega B97X-D, and M06-2X-is tested to calculate the structure of the dimer, the value of binding energy, and molecular nonlinear optical characteristics. According to the QTAIM analysis, the presence of bond critical points is revealed in the intermolecular region, the signs and values of topological characteristics giving evidence for the noncova-lent van der Waals interaction between the chromophores. The formation of stacks results in moderate increase of dimer static first hyperpolarizability as compared to that of a single chromophore, the effect depending on the relative shift of the chromophores in dimer. In a special case of greatly shifted chromophores, this enhancement of the first hyperpolarizability becomes appreciable and achieves 72%. (C) 2015 Wiley Periodicals, Inc.