Behavior of intermolecular interactions in -glycine under high pressure

Shinozaki, Ayako*; Komatsu, Kazuki*; Kagi, Hiroyuki*; Fujimoto, Chikako*; Machida, Shinichi*; Sano, Asami   ; Hattori, Takanori   

Pressure-response on the crystal structure of deuterated -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. Neutron diffraction measurements indicated the distance of the intermolecular DO bond along with the -axis increase with compression up to 6.4 GPa. The distance of another DO bond along with the -axis decreased with increasing pressure, and became the shortest intermolecular hydrogen bond above 3 GPa. In contrast, the lengths of the bifurcated N-DO and C-DO hydrogen bonds, which are formed between the layers of the -glycine molecules along the -axis, decreased significantly with increasing pressure. The decrease of the intermolecular distances resulted in the largest compressibility of the -axis, compared to the other two axes. Hirshfeld analysis suggested that the reduction of the void region size, rather than shrinkage of the strong N-DO hydrogen bonds, occurred with compression.