ζ-Glycine: insight into the mechanism of a polymorphic phase transition

Craig Bull; Stefano de Gironcoli; Emine Küçükbenli; Simon Parsons; Cong Huy Pham; Helen Playford; Matthew  G. Tucker; Giles Flowitt-Hill

doi:10.1107/S205225251701096X

ζ-Glycine: insight into the mechanism of a polymorphic phase transition

Craig Bull, Stefano de Gironcoli, Emine Küçükbenli, Simon Parsons, Cong Huy Pham, Helen Playford, Matthew G. Tucker, Giles Flowitt-Hill

Research output: Contribution to journal › Article › peer-review

Abstract

Glycine is the simplest and most polymorphic amino acid, with five phases having been structurally characterised at atmospheric or high pressure. A sixth form, the elusive ζ-phase, was discovered over a decade ago as
a short-lived intermediate formed as the high-pressure ε-phase transformed to the γ-form on decompression. However, its structure has remained unsolved. Here we 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 by using the results of a crystal structure prediction procedure based on fully ab initio energy calculations combined with a genetic algorithm for searching phase-space. We also 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 RT yielded β
- glycine, the least stable of the known ambient-pressure polymorphs.

Original language	English
Journal	IUCrJ
Early online date	1 Sept 2017
DOIs	https://doi.org/10.1107/S205225251701096X
Publication status	E-pub ahead of print - 1 Sept 2017

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20170811 Parsons paper_v2Accepted author manuscript, 652 KBLicence: Creative Commons: Attribution (CC-BY)

A Local View of Dynamic Processes in Molecular Crystals
Parsons, S. (Principal Investigator)
STFC
1/10/13 → 30/09/14
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abstract = "Glycine is the simplest and most polymorphic amino acid, with five phases having been structurally characterised at atmospheric or high pressure. A sixth form, the elusive ζ-phase, was discovered over a decade ago as a short-lived intermediate formed as the high-pressure ε-phase transformed to the γ-form on decompression. However, its structure has remained unsolved. Here we 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 by using the results of a crystal structure prediction procedure based on fully ab initio energy calculations combined with a genetic algorithm for searching phase-space. We also 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 RT yielded β - glycine, the least stable of the known ambient-pressure polymorphs. ",

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AU - Bull, Craig

AU - de Gironcoli, Stefano

AU - Küçükbenli, Emine

AU - Parsons, Simon

AU - Pham, Cong Huy

AU - Playford, Helen

AU - Tucker, Matthew G.

AU - Flowitt-Hill, Giles

PY - 2017/9/1

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N2 - Glycine is the simplest and most polymorphic amino acid, with five phases having been structurally characterised at atmospheric or high pressure. A sixth form, the elusive ζ-phase, was discovered over a decade ago as a short-lived intermediate formed as the high-pressure ε-phase transformed to the γ-form on decompression. However, its structure has remained unsolved. Here we 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 by using the results of a crystal structure prediction procedure based on fully ab initio energy calculations combined with a genetic algorithm for searching phase-space. We also 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 RT yielded β - glycine, the least stable of the known ambient-pressure polymorphs.

AB - Glycine is the simplest and most polymorphic amino acid, with five phases having been structurally characterised at atmospheric or high pressure. A sixth form, the elusive ζ-phase, was discovered over a decade ago as a short-lived intermediate formed as the high-pressure ε-phase transformed to the γ-form on decompression. However, its structure has remained unsolved. Here we 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 by using the results of a crystal structure prediction procedure based on fully ab initio energy calculations combined with a genetic algorithm for searching phase-space. We also 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 RT yielded β - glycine, the least stable of the known ambient-pressure polymorphs.

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ζ-Glycine: insight into the mechanism of a polymorphic phase transition

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