433296 Diffraction Pattern Calculator (DPC) Toolkit: A User-Friendly Approach to Unit Cell Lattice Parameter Identification of 2D Grazing-Incidence Wide-Angle X-Ray Scattering Data

Monday, November 9, 2015
Exhibit Hall 1 (Salt Palace Convention Center)
Anna K. Hailey1, Anna M. Hiszpanski1, Detlef-M. Smilgies2 and Yueh-Lin Loo1, (1)Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, (2)Cornell High Energy Synchrotron Source, Cornell University, Ithaca, NY

DPC Toolkit is a user-friendly program for identifying unit cell lattice parameters that are consistent with experimentally-obtained 2D grazing-incidence wide-angle X-ray scattering, GIWAXS, patterns. Our program is compatible with data collected directly on polycrystalline thin films, the structure of which critically impacts maroscopic properties. The input requirements for DPC toolkit are minimal and easy-to-assemble from data sets collected with any position-sensitive detector, and the user is required to make as few initial assumptions about the crystal structure as possible. For this reason, the program does not account for structure factors, which presuppose knowledge of the occupied lattice positions. Instead, the user may choose specific space groups to remove reflections that are forbidden due to symmetries of the unit cell. The user can also set the Miller index of the parallel plane, which allows the program to account for the preferential orientation of crystallites in thin films. By selecting Manual or Automatic modes of operation, the user can either visually match the positions of the experimental and calculated reflections by individually tuning the unit cell parameters, or have the program perform this process. The Automatic mode employs a “boundary-tightening” algorithm to narrow the ranges of possible unit cell lengths, based on the positions of key experimental reflections and physical constraints on the unit cell itself. We demonstrate the utility of this program through two examples: refining the lattice parameters of triethylsilylethynyl anthradithiophene, TES ADT, given its bulk crystal structure to obtain the lattice parameters of its thin-film crystal structure, and using a blind test to determine the lattice parameters of a fluorinated, contorted hexabenzocoronene, 16F-HBC.

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