Which charge definition for describing the crystal polarizing field and the χ⁽¹⁾ and χ⁽²⁾ of organic crystals?

Abstract

The impact of atomic charge definition for describing the crystal polarizing electric field has been assessed in view of predicting the linear and nonlinear optical susceptibilities of molecular crystals. In this approach, the chromophores are embedded in the electric field of its own point charges, which are evaluated through a self-consistent procedure including charge scaling to account for the screening of the dielectric. Once the crystal field is determined, dressed molecular polarizabilities and hyperpolarizabilities are calculated and used as input of an electrostatic interaction scheme to evaluate the crystal linear and nonlinear optical responses. It is observed that many charge definitions (i) based on partitioning the electron density (QTAIM), (ii) obtained by analyzing the quantum-chemical wavefunction (Mulliken, MBS, and NBO), and (iii) derived by fitting to the electrostatic potential (MK, CHelpG, and HLYGAt) give very consistent results and are equally valid whereas Hirshfeld partitioning and CM5 charge parametrizations underestimate the refractive indices and second-order nonlinear optical susceptibilities. An alternative approach omitting charge scaling is demonstrated to overestimate the different crystal optical properties. On the other hand, the molecule embedding approach provides results in close agreement with those calculated with a charge field obtained from periodic boundary condition calculations.

A Test of Various Partial Atomic Charge Models for Computations on Diheteroaryl Ketones and Thioketones

“…It is valid in our case, as evidenced by the negative MSE values of the Hirshfeld model in Figure 3. Both the MSE and RMSE values in Figure 3 indicate that the CM5 model outperforms the Hirshfeld one, which is also in accord with previous reports [9,44]. Furthermore, the CM5 model turns out to be slightly more accurate than the Mulliken one, and this observation is shared by the results of dipole moment calculations using the MG3S basis set [9].…”

Effects of Changing Substituents on the Non-Linear Optical Properties of Two Coumarin Derivatives

“…In the SM method, the atoms that form the surrounding molecules of the compounds are treated as point charges, since the interactions between molecules have a dominant electrostatic nature, taking into account long-range electrostatic effects [28,29]. Another alternative model to estimate χ (1) and χ (2) was proposed by Seidler and Champagne [30][31][32][33][34][35] with very good results.…”

Solid state characterization and theoretical study of non-linear optical properties of a Fluoro-N-Acylhydrazide derivative

“…As an example, we cite a recent work in which the authors used a polarization model to estimate the NLO properties, χ (1) and χ (2) of molecular crystals, with significant results when compared with the experimental data [38]. Other embedding schemes have also been designed for molecular crystals [39–43]. …”