溶液结构的同步辐射反射法研究——径向分布函数解析

A Synchrotron Radiation Reflection Study of the Solution Structure—Analysis the Radial Distribution Function

摘要: 本文报道用北京同步辐射装置4W1C光束线Huber五圆测角仪同步辐射散射法精确测定和数据校正获得硫酸钠水溶液径向分布函数的结构解析方法。结构参数最小二乘法精修结果表明，溶液中水合Na+有2个水合层，第1水合层Na+-OH2 (I)距离为0.243 nm，配位数6.0；第2水合层距离为0.448 nm，配位数为13.3； 存在第一水合层， -H2O距离为0.374 nm，配位数为9.1；水合硫酸根原子团中氧原子与水分子的作用距离和配位数分别为OS-W(1)，OS-W(2)，OS-W(3)，OS-W(4)距离依次为0.283，0.322，0.375和0.486 nm，配位数除OS-W(2)为12.9，其余都在8左右；除此之外溶液中还存在 接触离子对，Na-S距离为0.348 nm，配位数0.20，与晶体结构比较证实 以单齿形式配位到Na+；水共享离子对Na+-W- 中Na-S距离精修为0.491 nm，配位数0.62。精修的R因子为0.16，表明获得了很好的精修结果。

Abstract: A structure analysis method is reported in this paper. The accurate measurement and data correction of sodium sulfate liquid structure to obtain the radial distribution function by X-ray scattering with a five-circle goniometer in of the 4W1C beam line of Beijing Synchrotron Radiation Facility(BSRF I). The least squares refinement of structural parameters results show that the first hydration shell distance of Na+-OH2(I) is 0.243 nm, the hydration number is 6.0. The second hydration distance is 0.448 nm and the hydration number is 13.3. Sulfate ion has the first hydration layer, the hydration distance of -H2O is 0.374 nm, the coordination number (CN) is 9.1. The distance and CN of oxygens in with H2O, OS-W(1), OS-W(2), OS-W(3), OS-W(4), are 0.283, 0.322, 0.375 and 0.486 nm, respectively. Their CN 8.0 except the CN of OS-W(2) 12.9. Contact ion pairs also exist in the solution, the Na-S distance is 0.348 nm, and the CN is 0.20. We compared the structure with the crystal structure and confirmed that anion coordinated with Na+ ions in the mono-dentate form. The Na-S distance of water sharing ions Na+-W- is 0.491 nm, CN is 0.62. The R factor of the refinement 0.16 demonstrates a satisfactory calculation results.