Anion reorientation in an ion conducting plastic crystal – coherent quasielastic neutron scattering from sodium ortho-phosphate

Coupled anion and cation dynamics of silver orthophosphate in the picosecond range

“…It is found in the same range as for other ion conducting rotor phases, e.g., sodium orthophosphate (0.18 eV, [13,14]) or lithium sodium sulfate (0.13 eV, [25]). The dynamics monitored in our neutron data are consistently explained as isotropic anion rotational diffusion; the Q-dependent quasielastic intensities suggest that silver ions are involved in this reorientation.…”

“…Cation and anion dynamics in cubic Na 3 PO 4 have previously been analyzed by NMR techniques [11,12] and quasielastic neutron scattering [13][14][15][16]. Three dynamic processes could be detected in sodium orthophosphate: a fast anion reorientation around one of the C 3 axes parallel to 〈100〉, a slow reorientation of that C 3 axis and a jump diffusion process of sodium cations via empty lattice sites.…”

Plastic crystal behaviour in tetraethylammonium dicyanamide

“…This became known as Timmermans' criteria [6]. In later years, interest grew in plastic crystal behaviour in inorganic salts such as Li 2 SO 4 [5,11,12] and Na 3 PO 4 [13][14][15], which were investigated briefly as possible electrolyte materials. Studies on a range of organic molecular plastic crystals have further investigated the contributions to the entropy changes at the solid to plastic and plastic to liquid transitions.…”

Structure and dynamics of the plastic crystal tetramethylammonium dicyanamide—a molecular dynamics study☆

“…); for a material to exhibit plastic mechanical properties, its final entropy of melting, ΔS f , should be less than 20 J K −1 mol −1 [6]. In the 1980s, some inorganic salts were also found to exhibit rotator phases as well as plastic behaviour, for example, Li 2 SO 4 and Na 3 PO 4 , where a "paddle-wheel" rotation of the anions while fixed on their lattice sites was suggested as the cause of the long-range translational motion of the Li + and Na + cations [7,8].…”