Hydrogen bond reorientations driven phase transitions leading to dielectric anomaly in bis(glycinium)oxalate at high pressure and low temperature

Glycine complexes are of immense importance to fundamental science and technological applications. Bis(glycinium)oxalate is stabilized by an unusually strong hydrogen bond at ambient conditions in a centrosymmetric crystal structure. Here, using high pressure and low temperature infrared spectroscopic studies, supported by first principles density functional theory calculations, we present the mechanism of phase transformation in dense Bis(glycinium)oxalate, both at a pressure of 1.7 GPa and at temperatures below 50 K. The transition is governed by reorientations in strong hydrogen bonding network mediated by displacements in carboxylate ions, which modifies glycine conformation driving the loss of inversion symmetry. Further, we have carried out dielectric measurements, which show that the phase transformation is accompanied with a dielectric transition in the non-centrosymmetric phase of the crystal, making it a potential candidate to search for a new ferroelectric material in glycine family.