The application of Rietveld analysis to crystal structures of titanyl phthalocyanine

Terry Bluhm

doi:10.1117/12.2322225

1 May 1992 The application of Rietveld analysis to crystal structures of titanyl phthalocyanine

Terry Bluhm

Proceedings Volume 1670, Color Hard Copy and Graphic Arts; (1992) https://doi.org/10.1117/12.2322225
Event: SPIE/IS&T 1992 Symposium on Electronic Imaging: Science and Technology, 1992, San Jose, CA, United States

Abstract

This paper discusses the use of Rietveld analysis to solve crystal structures of titanyl phthalocyanines. Rietveld analysis is based on whole pattern fitting in which every point in the x-ray powder diffraction pattern is used as a measure of one or more Bragg diffraction peaks. Thus the refinement of relatively complicated crystal structures from x-ray patterns containing a relatively small number of resolved diffraction peaks is enabled. Various profile-fitting functions used in Rietveld analysis were parameterized and tested against known crystal structures of type I and type II titanyl phthalocyanine. It was found that a split Pearson VII function was found to best correct for preferred orientation effects observed in the x-ray patterns. The final goodness-of-fit parameters were R(Bragg) = 0.17 and 0.13 for type I and type II structures, respectively. A computer program was used to generate several unit cells for type IV titanyl phthalocyanine. These unit cells were tested by stereochemical packing analysis to first determine which unit cells allowed for good intermolecular packing arrangements. Energy minimized models were then used as phasing models for Rietveld refinement. A triclinic structure with space group P-1 having an x-ray goodness-of-fit parameter R(Bragg) = 0.24 was proposed as the most probable crystal structure for type IV titanyl phthalocyanine. The unitcell parametersarea = 1.083 nm, b = 1.312 nm, c = 0.996 nm, alpha = 72.28 degrees, beta = 77.25 degrees and gamma = 104.48 degrees. There are two molecules in the unit cell related by a center of inversion.

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Terry Bluhm "The application of Rietveld analysis to crystal structures of titanyl phthalocyanine", Proc. SPIE 1670, Color Hard Copy and Graphic Arts, (1 May 1992); https://doi.org/10.1117/12.2322225

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