高温及超临界条件下MgCl_2与CaCl_2水溶液中离子水化与缔合的量子化学计算  

Quantum Chemical Calculations on the Hydration and Association of MgCl_2 and CaCl_2 Solutions at High and Supercritical Temperatures

作　　者：丁皓[1] 朱宇[1] 王俊[1] 陆小华[1] 马晶[2] 

机构地区：[1]南京工业大学化工学院,南京210009 [2]南京大学化学系理论与计算化学研究所,南京210093

出　　处：《化学学报》2004年第14期1287-1292,J002,共7页Acta Chimica Sinica

基　　金：国家自然科学基金 (No .2 0 3760 32 );国家杰出青年科学基金 (No .2 992 561 6);国家自然科学重点基金(No .2 0 2 360 1 0 );江苏省自然科学基金 (No.BK971 2 4 )资助项目

摘　　要：对NaCl等碱金属水溶液的研究表明 ,室温条件下 ,离子在溶液中以水合形式存在 ,而在高温及超临界时 ,阴阳离子将结合成为离子对 .采用量子化学计算 ,研究了MgCl2 与CaCl2 水溶液中水化与缔合的情况 .通过Gaussian 98软件包计算了阳离子的水化自由能以及离子对的生成能 ,从而获得水合离子与离子对的热力学稳定性及其随温度、压力的变化情况 .通过比较热力学稳定性 ,考察了两种溶液中水化与缔合的变化情况 .研究结果表明 ,MgCl2 与CaCl2 水溶液中离子水化与缔合的变化趋势与碱金属溶液基本一致 ,但是存在一个过渡区域 ,该区域内离子对与水合离子共存 ,因此需要采用不同于碱金属溶液的方法处理MgCl2 与CaCl2 水溶液 .Studies on aqueous alkali metal solutions, especially NaCl solution, have shown that most ions exist in a hydrated form at ambient temperatures and ion pairs dominate at elevated temperatures. The quantum chemical calculations have been performed to investigate the hydration and association in aqueous MgCl2 and CaCl2 solutions. The hydration free energies of cations and formation energies of ion pairs were calculated by software package Gaussian 98 under different conditions. These calculations give the thermodynamic stabilities of hydrated cations and ion pairs and the variation depending on temperature and pressure. By comparing the stabilities of hydrated cation and ion pair, the variation for hydration and association can be determined. The results indicate that the tendencies for hydration and association in MgCl2 and CaCl2 solutions agree with those in alkali metal ion solutions, but there is a different area where ion pairs and hydrated ions coexist and both hydration and association have important influences on the solution. In this area, thermodynamic models for NaCl solution are not applicable and new models must be established for MgCl2 and CaCl2 solutions.

关 键 词：氯化钙水溶液 氯化镁水溶液 离子水化 离子缔合 量子化学 高温 超临界 

分 类 号：O645[理学—物理化学]