Exploring the phase space of H-bond driven dynamics of ionic plastic crystals via variable temperature and pressure powder diffraction studies

Ionic plastic crystals (IPCs) are materials comprised completely of ions, which at room temperature, are solids with significant disorder in the crystal structure. As a result, these materials have a rich landscape of temperature driven solid-solid phase transitions. Recent discoveries of colossal barocaloric effects in molecular plastic crystals (MPCs) suggest that PCs in general could have a huge impact on the future of solid-state cooling technology. One of the many advantages of IPCs is the ability to tailor their properties by modifications to the cation and/or anion. We therefore wish to use neutron powder diffraction to study the phase behaviour of the CHOM-X family as a function of temperature and pressure. We wish to understand the structural origins of these thermal effects. In particular, we seek to understand the long-range structural symmetry, local molecular orientations and most interestingly the cation-anion cooperativity in inducing these phase transitions.