氯化钠水溶液结构的研究

利用上海光源(SSRF)的第三代同步辐射光源测定室温下摩尔浓度分别为0.172 mol/L、0.343 mol/L、0.699 mol/L、1.064 mol/L、2.832 mol/L、3.910 mol/L、5.289 mol/L的NaCl水溶液的X射线散射数据。由X射线散射数据可知，随着NaCl水溶液浓度的增大，X射线散射曲线的特征峰由12.6°到13.4°发生偏移。运用Pair Distribution Function(PDF)理论对X射线散射数据进行处理，得到了不同浓度NaCl水溶液及纯水的差值对分布函数，其中的O-O峰随着浓度的增大逐渐分裂为两峰，O-O峰位在0.282 nm处。利用分子动力学模拟研究不同浓度的NaCl水溶液，表明Na+、Cl-的引入对水分子的氢键结构有一定的破坏，当浓度大于15%时，这种效果尤其明显。Na+、Cl-均存在两层水化层，各离子间配位数随浓度的增大而减少。H2O分子的自扩散系数远大于Na+和Cl-的自扩散系数，后两者的值随浓度的增大逐渐减少，Na+和Cl-的水化半径均随浓度增大而降低。

Study on the Structure of Sodium Chloride Aqueous Solution

X-ray scattering data of NaCl aqueous solution was measured by the third generation synchrotron light source of Shanghai Synchrotron Radiation Facility (SSRF). The molar concentrations of the solution were 0.172 mol/L, 0.343 mol/L, 0.699 mol/L, 1.064 mol/L, 2.832 mol/L, 3.910 mol/L, 5.289 mol/L respectively at room temperature. Based on the X-ray scattering results, when the concentrations of NaCl aqueous solution increased, the characteristic peaks shifted from 12.6o to 13.4o. The pair distribution functions of NaCl aqueous solution with different concentrations and pure water were obtained by Pair Distribution Function (PDF) theory. The O-O peak gradually split into two peaks with the increased concentration and the O-O peak was at 0.282 nm. The results obtained by molecular dynamic simulation indicated that the hydrogen bond structure of water molecules was destroyed by Na+ and Cl-. The effect was particularly evident when the concentration was higher than 15%. It was found that there were two hydrated shells around Na+ and Cl-. The coordination number, the self-diffusion coefficient and the hydration radius all decreased with the increased concentration. The self-diffusion coefficient of water molecules was much higher than that of Na+ and Cl-.