Use of Electron Diffraction and High-Resolution Imaging To Explain Why the Non-dipolar 1,3,5-Triamino-2,4,6-trinitrobenzene Displays Strong Powder Second Harmonic Generation Efficiency

Abstract

The structure of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) has been reinvestigated by a combination of electron diffraction, high-resolution imaging, simulations of electron diffraction patterns and images, and packing energy calculations. A new model is proposed that is capable of explaining the large second harmonic generation effect observed in TATB crystalline powder.

Crystal Engineering with Symmetrical Threefold Acceptor-Substituted Triaminobenzenes

“…We have recently shown that symmetrical trinitrotriaminobenzene ( two polymorphs, one of which is noncentrosymmetric (space group P3 1 ) and almost ideally suited for use in nonlinear optics. [15,16] In both polymorphs, graphitelike layer structures of approximate trigonal symmetry are found that arise from strong intra-and intermolecular hydrogen bonding (Scheme 2). In the centrosymmetric structure the layers are stacked antiparallel, whereas in the other they are stacked parallel, but with small displacements relative to each other.…”

Protein Degradation Vol. 2: The Ubiquitin‐Proteasome System. Edited by R. John Mayer, Aaron J. Ciechanover and Martin Rechsteiner.

“…X‐ray structure determination33 gave a \documentclass{article}\pagestyle{empty}\begin{document}$\mathrm{P}\bar{1}$\end{document} space group, while the crystal shows nonlinear optical activity that is incompatible with nonpolar structures. There have been several attempts to reconcile this apparent discrepancy between experiments 34–36. The conspicuous deviation between experimental structures and optimized SCMP‐NDDO cell parameters, especially that found in the calculation without symmetry restraints, also suggest that a noncentrosymmetric arrangement of layers results in a favorable packing of TATNBZ.…”

Structure determination to calculate nonlinear optical coefficients in a class of organic material

“…100 Å thick and several hundred Å long, becomes mandatory. We have been able to solve several unknown structures using two new methods, namely, simulation of electron diffraction patterns from suitable model structures [4][5][6][7][8] and maximum entropy combined with loglikelihood evaluation. [9][10][11] In this paper we study the molecular and crystallographic parameters relevant for second harmonic generation in a twodimensional molecule.…”