Neutron Diffraction Study on the Structure of Hydrated Li+ in Dilute Aqueous Solutions
Neutron Diffraction Study on the Structure of Hydrated Li+ in Dilute Aqueous Solutions
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DOI：
10.1021/acs.jpcb.7b12218
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发表时间：
2018-02-08
影响因子：
3.3
通讯作者：
Otomo, Toshiya
中科院分区：
文献类型：
--
作者：
Kameda, Yasuo;Maeda, Shunya;Otomo, Toshiya
用中子衍射方法测量了Li-6/Li-7同位素取代的1.0mol%（0.5mol/kg）LiCl和1.1mol%（0.56mol/kg）LiClO_4水溶液在D_2O中的结构，以了解Li ~+在更稀电解质溶液中的水合结构。一阶差分函数Delta（Li）（Q）通过最小二乘拟合程序进行分析，以获得Li+周围的短程结构参数。结果表明，对于1.0摩尔% LiCl水溶液，最近邻Li+中心点O（D2 O）距离r（LiO）和配位数n（LiO）分别为2.01 +/-0.02埃和5.9 +/-0.1。对于1.1mol%LiClO4水溶液，得到的值r（LiO）= 1.97 +/- 0.02埃和n（LiO）= 6.1 +/- 0.1。这些结果表明，Li+在稀溶液中的水化数接近6，远大于长期以来人们所认为的4。一个可能的解释是Li+的水化数随溶质浓度而变化。
Neutron diffraction measurements have been carried out for Li-6/Li-7 isotopically substituted aqueous 1.0 mol % (0.5 mol/kg) LiCl and 1.1 mol % (0.56 mol/kg) LiClO4 solutions in D2O to obtain structural insight concerning hydration structure of Li+ in more dilute electrolyte solutions. The first-order difference function, Delta(Li)(Q), was analyzed by means of the least squares fitting procedure to obtain short-range structural parameters around the Li+. It was revealed that the nearest neighbor Li+center dot center dot center dot O(D2O) distance, r(LiO), and the coordination number, n(LiO), for the aqueous 1.0 mol % LiCl solution are 2.01 +/- 0.02 angstrom and 5.9 +/- 0.1, respectively. The values, r(LiO) = 1.97 +/- 0.02 angstrom and n(LiO) = 6.1 +/- 0.1, are obtained for aqueous 1.1 mol % LiClO4 solution. These results indicate that the hydration number of Li+ in a dilute solution is close to 6, which is much larger than 4, which has long been believed. A possible explanation is that the hydration number of Li+ varies with the solute concentration.