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Bart Kahr, John Freudenthal, Shane Phillips, Werner Kaminsky: Herapathite. SCIENCE - Brevia 324 (2009) 1407
ORTEP Plot (50% probability) WinXMorph plot of morphology
Pre-prosessing version of paper link to original
(Authors Version posted here by permission of the AAAS for personal use, not for redistribution)
Chemistry World Blog
When Professor Bart Kahr was searching for systems with oriented molecules in crystalline or polymeric matrices he found that the molecular structure of the crystalline material, herapathite was never determined. Herapathite was then synthesized by Undergraduate student Shane Phillips and Graduate student John Freudenthal. The structure was solved on a Nonius FR590 Kappa X-ray diffractometer with Mo radiation by the departmental crystallographer Research Associate Professor Werner Kaminsky. The job turned out to be difficult with small and non-merohedrally twinned crystals to start with, and several different equally likely orthorhombic space groups were tried until a solution took shape. The molecules and waters were arranged as shown in the ORTEP above revealing a structure with open channels. Results are summarized in the supplementary material for which Werner Kaminsky signs responsibility, should there be any reason to complain. Professor Bart Kahr wrote the Brevia article which appeared in Science Magazine, demonstrating the importance of this material for optical applications including photography. Herapathite was used for large polarizers (Bernotar) for the Hasselblad camera in a process invented by F. Bernauer, involving supercooled solutions of herapathite most likely in Canada Balsam. The underlying Bernauer Patent was finally found by Werner Kaminsky after a lengthy search.
The Herapathite structure
Website with interactive structure plot
Bart Kahr, John Freudenthal, Werner Kaminsky