A reversible pressure-induced phase transition in β-glycine at 0.76GPa

High Pressure Raman Spectra of Amino Acid Crystals

“…Additionally, the transition is characterized by a rapid propagation of an interphase boundary accompanied by the crack formation in the crystal as verified by authors of Ref. (Goryainov et al, 2005). On decompression, the high pressure phase ('-glycine) transforms back to the -glycine without hysteresis (Goryainov et al, 2005), which is not a general result among amino acid crystals.…”

“…In fact, for other amino acid crystals it has been reported that the r(CO 2 -) is the most intense band in the 200 -700 cm -1 spectral range. However, for the other amino acids, differently from L-proline, the r(CO 2 -) mode is observed for wavenumber higher than 500 cm -1 (-glycine: 503 cm -1 (Dawson et al, 2005); L-alanine: 532 cm -1 ; L-valine, 542 cm -1 (Goryainov et al, 2005); DL-alanine, 543 cm -1 ; etc.). Finally, in the spectrum taken at 0.0 GPa we can observe a band at 574 cm -1 which was associated to a bending of CO 2 -, group.…”

“…(Goryainov et al, 2005). On decompression, the high pressure phase ('-glycine) transforms back to the -glycine without hysteresis (Goryainov et al, 2005), which is not a general result among amino acid crystals. While the  and forms of glycine crystallize in a monoclinic structure, respectively, with space groups P2 1 /n and P2 1 , -glycine crystallizes in a trigonal symmetry (P3 1 ) (Boldyreva et al, 2003a).…”

“…The -glycine has a crystal structure very similar to the -glycine, although this last polymorph is most stable and should be obtained from the -polymorph under humid conditions (Dawson et al, 2005). For -glycine it was observed through both Raman and polarizing spectroscopies a reversible phase transition at 0.76 GPa (Goryainov et al, 2005). Such a phase transition is accompanied by pronounced changes in the Raman spectra of the material, in particular by jumps and kinks at the curves of frequency versus pressure (for the band associated to NH 3 rock, the jump is higher than 10 cm -1 ).…”

Variable-temperature and variable-pressure studies of small-molecule organic crystals

“…Low-temperature Raman spectroscopy has recently confirmed the existence of low-temperature phase transition in the β-glycine. 67 Interestingly, a β α polymorphous transition could be induced by repeated temperature cycling in the vicinity of the low-temperature piezoelectric phase transition in the β-form. The directions of maximum and minimum lattice strain were related to the directions of weak and strong hydrogen bonds in the structures.…”