A structural phase transition and molecular motions in (C2H5NH3)2[ZnBr4] studied by 1H NMR and X-ray diffraction

The H-1 NMR spin-lattice relaxation times and the second moments of the resonance linewidth were measured as a function of temperature in (C2H5NH3)(2)[ZnBr4]. The crystal structure at 295 K was determined to be orthorhombic with space group of P2(1)2(1)2(1) by the single-crystal X-ray diffraction method. The crystal undergoes a 1st order structural phase transition at T-c = 300 K. which is driven by the disordering of cationic orientations. The crystal structure above T-c is inferred to be orthorhombic with space group of Pmnb(D-2h(16)).