“…); 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].…”