High pressure phase transitions in diglycine perchlorate: a Raman spectroscopic study

We report high pressure studies on an organic perchlorate system diglycine perchlorate (DGPCl) up to 15 GPa. Single crystals of DGPCl were studied using high pressure Raman spectroscopy, which show discontinuous spectral changes at two pressures across ~1.8 and ~9 GPa. While the low pressure phase transition is primarily governed by the reorientational changes in organic groups and the corresponding hydrogen bonds, the high pressure transition involves substantial changes in Raman spectroscopic features of the perchlorate group. The splitting of the characteristic and the most intense Raman mode, i.e., perchlorate symmetric stretching mode, above 9 GPa suggests modifications in perchlorate group local structure. The structural changes are found to be reversible upon pressure release.