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The NMR Study of the disorder in lithium iodide monohydrate and monodeuterate

1969; Elsevier BV; Volume: 1; Issue: 1 Linguagem: Inglês

10.1016/0022-2364(69)90008-0

1557-8968

H. Chihara, Tsuyoshi Kawakami, Gen Soda,

Advanced NMR Techniques and Applications

From resonances of proton, deuteron and lithium in LiI·H2O and/or LiI·D2O between 80 and 400 °K, the statistical disorder above 280°K in this cubic perovskite structure was found to be dynamic: the water molecules are reorienting themselves at the body-center position with an activation energy of 13.4 kcal/mole and lithium ions are diffusing among face-center positions with an energy barrier of 13.5 kcal/mole. The absorption lines of H and Li are broadened below about 220°K where the disorder is frozen in a random way. There is correlation between the motions of water and lithium. X-ray diffraction gives the same pattern at 180°K as at room temperature. Differential thermal analysis failed to detect a phase transition between 20°K and the melting point (400°K). Dielectric loss measurements also gave an activation energy of 12.7 kcal/mole for the reorientation of water. The “cross-narrowing” phenomenon is discussed, in which two different nuclear species undergo width-transitions in the same temperature region, one width change enhancing the other. The dehydration pressures of the hydrate were measured between 81 and 130°C; log P (Torr) =−(3.82/T)+10.3 with the heat of dehydration 17.5 kcal/mole.