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. 2017 Sep 1;4(Pt 5):569-574.
doi: 10.1107/S205225251701096X.

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

Craig L Bull  1 , Giles Flowitt-Hill  1   2 , Stefano de Gironcoli  3 , Emine Küçükbenli  3 , Simon Parsons  2 , Cong Huy Pham  3   4 , Helen Y Playford  1 , Matthew G Tucker  1   5
Affiliations

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

Craig L Bull et al. IUCrJ. .

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 ζ phase, was discovered over a decade ago as a short-lived intermediate which formed as the high-pressure ∊ 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 fully ab initio energy 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.

Keywords: amino acids; crystal structure prediction; crystallization under non-ambient conditions; neutron diffraction; phase transitions; polymorphism.

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Figures

Figure 1
Figure 1
Enthalpy versus volume distribution for all the structures obtained via ab initio crystal structure search within the lowest 2 kJ mol−1 range of the most stable γ phase. Crowding around each polymorph indicates multiple encounters with the same phase during the phase-space exploration.
Figure 2
Figure 2
(a) Rietveld fit of the neutron powder diffraction pattern of ζ-glycine at 100 K (blue = observed, red = calculated). In addition to the peaks from ζ-glycine, the pattern also shows the presence of residual ∊- and a trace of γ-glycine. Other peaks arise from the sample environment, namely the lead pressure marker and the Al2O3 and ZrO2 components of the anvils of the pressure cell. (b) Rietveld fit of the neutron powder diffraction pattern of β-glycine (contaminated with ζ- and a trace of γ-glycine) at 290 K. A 1 Å d spacing approximates to 4837 µs in time-of-flight.
Figure 3
Figure 3
Intermolecular interactions in ζ-glycine. (a) Layers formed in the ac plane, viewed along b. (b) Stacking of the layers, viewed along c.
See this image and copyright information in PMC

References

    1. Berland, K., Cooper, V. R., Lee, K., Schröder, E., Thonhauser, T., Hyldgaard, P. & Lundqvist, B. I. (2015). Rep. Prog. Phys. 78, 066501. - PubMed
    1. Boldyreva, E. V., Ivashevskaya, S. N., Sowa, H., Ahsbahs, H. & Weber, H.-P. (2005). Z. Kristallogr. Cryst. Mater. 220, 50–57.
    1. Bordallo, H. N., Boldyreva, E. V., Buchsteiner, A., Koza, M. M. & Landsgesell, S. (2008). J. Phys. Chem. B, 112, 8748–8759. - PubMed
    1. Brandenburg, K. (2004). DIAMOND. Crystal Impact GbR, Bonn, Germany.
    1. Bull, C. L., Funnell, N. P., Tucker, M. G., Hull, S., Francis, D. J. & Marshall, W. G. (2016). High. Press. Res. 36, 493–511.