Behavior of intermolecular interactions in α-glycine under high pressure

Abstract

Pressure-response on the crystal structure of deuterated α-glycine was investigated at room temperature, using powder and single-crystal X-ray diffraction, and powder neutron diffraction measurements under high pressure. No phase change was observed up to 8.7 GPa, although anisotropy of the lattice compressibility was found. No significant changes in the compressibility and the intramolecular distance between non-deuterated α-glycine and deuterated α-glycine were observed. Neutron diffraction measurements indicated the distance of the intermolecular D⋯O bond along with the c-axis increased with compression up to 6.4 GPa. The distance of another D⋯O bond along with the a-axis decreased with increasing pressure and became the shortest intermolecular hydrogen bond above 3 GPa. In contrast, the lengths of the bifurcated N-D⋯O and C-D⋯O hydrogen bonds, which are formed between the layers of the α-glycine molecules along the b-axis, decreased significantly with increasing pressure. The decrease of the intermolecular distances resulted in the largest compressibility of the b-axis, compared to the other two axes. The Hirshfeld analysis suggested that the reduction of the void region size, rather than shrinkage of the strong N-D⋯O hydrogen bonds, occurred with compression.

High-pressure polymorphism inl-threonine between ambient pressure and 22 GPa

“…3 The crystal structure has been determined by X-ray single-crystal and neutron powder diffraction at 6.2 (ref. 4) and 6.4 GPa, 5 respectively. Very recent angle-dispersive X-ray diffraction measurements show that the phase persists to 50 GPa.…”

“…There is a single-crystal to single-crystal phase transition at 18.2 GPa which reduces the space group symmetry from P2 1 2 1 2 1 , to P2 1 , though the unit cell metrics are similar either side of the transition. The structure was modelled with a twofold axis about a as a twin law, but the twin fraction refined to 0.05 (5). The orthorhombic cells of the structure below 18.2 GPa were placed in a non-standard setting to match that of the monoclinic phase in order to facilitate comparisons between phases.…”

“…77 At 17.1 GPa the unit cell dimensions of phase II are a = 4.768(4), b = 12.883IJ10), c = 6.353(7) Å, V = 390.2(6) Å 3 , representing a volume reduction of 28% compared to the ambient-pressure structure. The cell dimensions after the transition to phase III at 18.2 GPa are a = 4.735 (5), b = 12.823 (13), c = 6.275(8) Å, β = 91.14IJ3)°, V = 380.9 (8) Å 3 , so that after the phase transition, though the 2 1 operations along the a and c directions are lost, the translational symmetry of the lattice is preserved and Z is still equal to four, but Z′ = 2. The structure remains in phase III up to 22.3 GPa, the highest pressure reached in this study.…”

Weak interactions in crystals: old concepts, new developments

“…It was also found that the double-well potential of a hydrogen bond is transformed into a single well under pressure. A neutron diffraction study of deuterated -glycine up to 8.7 GPa (Shinozaki et al, 2018) showed non-uniform changes of hydrogen bonds on weak interactions in crystals compression, with a large shrinking of bifurcated N-DÁ Á ÁO and C-DÁ Á ÁO bonds, while strong linear N-DÁ Á ÁO bonds change little and in both senses, but in any case, Hirshfeld analysis revealed that the compression was due mainly to squeezing out of voids rather than shrinkage of these bonds. Fanetti et al (2018) analysed the role of (classical) hydrogen bonds under pressure, in favouring or hindering solid-state reactions (e.g.…”

The structural, electronic and optical properties of γ-glycine under pressure: a first principles study

“…High pressure is one method which can be used to regulate and control the electronic structure and optical properties of many materials. [4][5][6]12,24,26,27,30,31,36,37 From previous observations, pressure has been shown to drastically alter the properties of amino acids, and can induce phase transitions. 13,32 Thus, crystal structures that experience high pressures may result in sufficiently different, and potentially applicable changes in their optical and electronic properties.…”