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Persistent URL http://purl.org/net/epubs/work/34839663
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Record Id 34839663
Title zeta-Glycine: insight into the mechanism of a polymorphic phase transition
Abstract Glycine is the simplest and most polymorphic amino acid, with five phases having been structurally characterized at atmospheric or high pressure. A sixth form, the elusive $ėta$ phase, was discovered over a decade ago as a short-lived intermediate which formed as the high-pressure $\varepsilon$ phase transformed to the $\gamma$ form on decompression. However, its structure has remained unsolved. We now report the structure of the $ėta$ phase, which was trapped at 100K enabling neutron powder diffraction data to be obtained. The structure was solved using the results of a crystal structure prediction procedure based on fully \it ab initio energy calculations combined with a genetic algorithm for searching phase space. We show that the fate of $ėta$-glycine depends on its thermal history: although at room temperature it transforms back to the $\gamma$ phase, warming the sample from 100K to room temperature yielded $ėta$-glycine, the least stable of the known ambient-pressure polymorphs.
Organisation ISIS , ISIS-PEARL , STFC
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Language English (EN)
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Journal Article IUCrJ 4, no. 5 (2017): 569-574. doi:10.1107/S205225251701096X 2017