%0 Journal Article
%T <br>
%A 周永全
%A 山口敏男
%A 房春晖
%A 房艳
%A 曾我良枝
%J 物理化学学报
%D 2018
%R 10.3866/PKU.WHXB201709111
%X 采用X射线散射法研究了RbCl和CsCl水溶液的结构，利用基于经验势的结构精修(EPSR)方法获得了溶液中的水合Cl-、Rb+、Cs+、离子缔合及本体水的对径向分布函数、配位数分布及空间密度分布(3D结构)等结构信息。在水溶液中，Cl-具有相对稳定的6水合结构，其水合距离为0.321 nm，外加阳离子对其水合作用的影响不明显。7.3 ± 1.4个水分子与Rb+水合，其特征水合距离为0.297 nm，8.4 ± 1.6个水分子与Cs+水合其水合距离为0.312 nm。Cs+不具有第二水合层，而Rb+表现出了更强的水合能力，具有较明显的第二水合层。Cl-、Rb+及Cs+常被认为是“结构破坏”型离子。从微观角度来看这种所谓的“结构破坏”主要体现在破坏了本体水分子的第二水合层保持四面体构型的趋势。RbCl和CsCl水溶液中部分存在着Rb-Cl和Cs-Cl直接接触离子对，在1.0 mol·dm-3的溶液中Rb-Cl及Cs-Cl的特征距离分别为0.324和0.336 nm，溶剂分割离子对的距离则都在0.6 nm左右。相对于Cs+，Rb+与Cl-离子之间表现出了更强的缔合能力。<br>X-ray scattering measurements were performed on 1.0 mol·dm-3 RbCl and CsCl aqueous solutions. The X-ray structure factors were subjected to empirical potential structure refinement to extract detailed structural information on hydrated Cl-, Rb+, Cs+, and ion association, as well as bulk water, in terms of the individual site-site pair correlation functions, coordination number distributions, and spatial density functions (three-dimensional structure). Cl- is found to have a relatively stable six-fold coordination of water molecules with a Cl--H2O distance of 0.321 nm, and without a significant cation effect on its local structure. Rb+ is surrounded on an average by 7.3 ± 1.4 water molecules with a Rb+-H2O distance of 0.297 nm, whereas 8.4 ± 1.6 water molecules hydrate Cs+ at a Cs+-H2O distance of 0.312 nm. It is likely that Rb+ has a stronger hydration shell than Cs+, as evidenced by the presence of the second hydration shell of the former. Contact ion-pairs are partially formed in both solutions and characterized by the Rb+-Cl- and Cs+-Cl- distances of 0.324 nm and 0.336 nm. The solvent-separated ion pairs for both ions are discernible at around 0.6 nm. Rb+ has a stronger electrostatic interaction and hence a relatively stronger ion association with Cl- than Cs+
%U http://www.whxb.pku.edu.cn/CN/Y2018/V34/I5/483