QTAIM-Based Scheme for Describing the Linear and Nonlinear Optical Susceptibilities of Molecular Crystals Composed of Molecules with Complex Shapes

Abstract

The Quantum Theory of Atoms in Molecules (QTAIM) to distribute the molecular polarizability tensors over submolecular sites is employed to improve the prediction of local field tensors of molecular crystals and therefore of their linear and second-order nonlinear optical susceptibilities. This extension of the two-step multiscale procedure is intended to better describe crystals built of molecules having complex shapes. When combined with a simple charge embedding approach to account for the crystal field effects on the molecular (hyper)polarizabilities, this QTAIM local field theory (Q-LFT) approach is efficient to predict the χ(1) and χ(2) tensor components. Moreover, it does not require substantial computational resources because the largest calculations are performed on the individual molecules. This is illustrated by considering derivatives of (S)-2-(α-methylbenzylamino)-5-nitropyridine (MBANP) as well as 2-methyl-4-nitroanline (MNA), which is a prototypical push–pull π-conjugated compound. In the la...