Molecular motions and phase changes in the perovskite-type compound (C10H21NH3)2ZnCl4

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Abstract
A virgin sample of polycrystalline (C10H21NH3)2ZnCl4 shows two phase transitions, at 284 K and 363 K. In the low-temperature phase threefold reorientations of methyl and NH3 groups dominate the nuclear magnetic resonance relaxation results. The motion of the NH3 groups can be described as a three-fold jump among three potential minima of which one is shallower than the other two. In the intermediate temperature phase a defect motion of chain ends has been identified. In the high-temperature phase the spacing between adjacent layers of ZnCl4 tetrahedra is increased by ∼ 16% due to the non-intercalation of the chains. In this phase the chains experience a high degree of mobility, which is partly due to the diffusion of chain defects along the chain. On cooling the sample from the high-temperature phase, it transforms to the intermediate phase, but the transition to the low-temperature phase is absent.