ζ-Glycine: insight into the mechanism of a polymorphic phase transition
- Harwell Science and Innovation Camus, Didcot (United Kingdom). Rutherford-Appleton Lab. ISIS Facility
- Harwell Science and Innovation Camus, Didcot (United Kingdom). Rutherford-Appleton Lab. ISIS Facility; Univ. of Edinburgh, Scotland (United Kingdom). School of Chemistry and Centre for Science at Extreme Conditions
- Scuola Internazionale Superiore di Studi Avanzati, Trieste (Italy)
- Univ. of Edinburgh, Scotland (United Kingdom). School of Chemistry and Centre for Science at Extreme Conditions
- Scuola Internazionale Superiore di Studi Avanzati, Trieste (Italy); Univ. of California, San Diego, CA (United States). Dept. of Chemistry and Biochemistry
- Harwell Science and Innovation Camus, Didcot (United Kingdom). Rutherford-Appleton Lab. ISIS Facility; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
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 ζ phase, was discovered over a decade ago as a short-lived intermediate which formed as the high-pressure ϵ phase transformed to the γ form on decompression. However, its structure has remained unsolved. We now report the structure of the ζ phase, which was trapped at 100 K enabling neutron powder diffraction data to be obtained. The structure was solved using the results of a crystal structure prediction procedure based on fullyab initioenergy calculations combined with a genetic algorithm for searching phase space. We show that the fate of ζ-glycine depends on its thermal history: although at room temperature it transforms back to the γ phase, warming the sample from 100 K to room temperature yielded β-glycine, the least stable of the known ambient-pressure polymorphs.
- Research Organization:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- Grant/Contract Number:
- AC05-00OR22725
- OSTI ID:
- 1625820
- Journal Information:
- IUCrJ, Vol. 4, Issue 5; ISSN 2052-2525
- Publisher:
- International Union of CrystallographyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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