First principles crystal engineering of nonlinear optical materials. I. Prototypical case of urea

Abstract

The crystalline materials with nonlinear optical (NLO) properties are critically important for several technological applications, including nanophotonic and second harmonic generation devices. Urea is often considered to be a standard NLO material, due to the combination of non-centrosymmetric crystal packing and capacity for intramolecular charge transfer. Various approaches to crystal engineering of non-centrosymmetric molecular materials were reported in the literature. Here we propose using global lattice energy minimization to predict the crystal packing from the first principles. We developed a methodology that includes the following: (1) parameter derivation for polarizable force field AMOEBA; (2) local minimizations of crystal structures with these parameters, combined with the evolutionary algorithm for a global minimum search, implemented in program USPEX; (3) filtering out duplicate polymorphs produced; (4) reoptimization and final ranking based on density functional theory (DFT) with many-body dispersion (MBD) correction; and (5) prediction of the second-order susceptibility tensor by finite field approach. This methodology was applied to predict virtual urea polymorphs. After filtering based on packing similarity, only two distinct packing modes were predicted: one experimental and one hypothetical. DFT + MBD ranking established non-centrosymmetric crystal packing as the global minimum, in agreement with the experiment. Finite field approach was used to predict nonlinear susceptibility, and H-bonding was found to account for a 2.5-fold increase in molecular hyperpolarizability to the bulk value.

Electron density learning of non-covalent systems

“…16 Moreover, analyzing the deformation of r(r) in the presence of an external eld provides access to another set of fundamental properties, namely molecular static (hyper) polarizabilities and, thus, to the computation of Raman spectra 17 and non-linear optical properties. [18][19][20][21] The natural representation of the electron density in real space makes it especially suitable for accessing spatial information about structural and electronic molecular properties, including X-ray structure renement [22][23][24][25][26][27] and representations using scalar elds. 6 Routinely used examples include the quantum theory of atoms in molecules (QTAIM), 28,29 the density overlap region indicator (DORI), 30 and the non-covalent interaction (NCI) index.…”

Virtual Tensile Test for Brittle, Plastic, and Elastic Polymorphs of 4-Bromophenyl 4-Bromobenzoate

“…Many research groups, − including ours, − have demonstrated how density functional theory (DFT) in conjunction with global minimization methods for the lattice energy may serve as powerful tools in crystal structure predictions (CSP). The latter include evolutionary algorithms implemented in USPEX .…”

Synthesis, structural characterization, and density functional theory calculations of the two new Zn (II) complexes as antibacterial and anticancer agents with a neutral flexible tetradentate pyrazole‐based ligand

“…These remarkable values are comparable to urea with β 0 = 72.2 au. Urea is conventionally known as a standard NLO material, [ 68 ] and thereby the sensitized complexes have NLO response nearly 5 times greater than urea molecule.…”