KNO_(3)溶液结构:密度泛函理论和分子动力学研究  

Structure of KNO_(3)Solutions:Density Functional Theory and Molecular Dynamics

作　　者：刘红艳[1] 景转芳 王广国 柴珂珂 朱发岩[1] 周永全[1] LIU Hong-yan;JING Zhuan-fang;WANG Guang-guo;CHAI Ke-ke;ZHU Fa-yan;ZHOU Yong-quan(Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources,Key Laboratory of Salt Lake Resources Chemistry of Qinghai Province,Qinghai Institute of Salt Lakes,Chinese Academy of Sciences,Xining,810008,China;University of Chinese Academy of Sciences,Beijing,100049,China)

机构地区：[1]中国科学院青海盐湖研究所,盐湖资源综合高效利用重点实验室,青海省盐湖资源化学重点实验室,青海西宁810008 [2]中国科学院大学,北京100049

出　　处：《盐湖研究》2022年第4期128-145,共18页Journal of Salt Lake Research

基　　金：青海省盐湖资源化学重点实验室创新平台建设专项(2022-ZJ-Y06);青海盐湖所青年交叉团队项目(ISLJCTD-2022-04);国家自然科学基金面上项目(21973106)。

摘　　要：基于密度泛函理论,采用ωB97XD方法和6-311++G(d,p)基组,系统研究了[K(H_(2)O)_(n)]+,[NO_(3)(H_(2)O)_(n)]-和KNO_(3)(H_(2)O)_(n)水合团簇的结构和性质;并结合经典分子动力学、OPLS-AA全原子力场以及SPC/E水模型模拟了不同水盐比(WSR)KNO_(3)溶液,目的在于深入理解KNO_(3)溶液中K^(+)和NO_(3)^(-)的微观水合结构,以及K^(+)-NO_(3)^(-)离子间缔合作用特征。研究发现,对于KNO_(3)(H_(2)O)_(n)(n=6,8,10和12)水合团簇,K^(+)第一水合层稳定结构为四、五和六水合结构,其中五水合结构最稳定。K^(+)和NO_(3)^(-)主要以溶剂共享离子对形式存在。随着团簇尺寸减小,直接接触离子对(CIP)物种出现。同时,分子动力学模拟证实KNO_(3)溶液中形成了直接接触K^(+)-NO_(3)^(-)离子对,且随着溶液浓度增加,CIP物种形成需越过更大能垒。以上结果表明在KNO_(3)稀溶液中主要存在物种为水合K^(+)和NO_(3)^(-),随浓度增大,单齿直接接触离子对(MCIP)逐渐出现。在高浓溶液或过饱和溶液中,K^(+)-NO_(3)^(-)离子缔合主要以单齿CIP和少量双齿CIP结构存在。The structures and properties of[K(H_(2)O)_(n)]+,[NO_(3)(H_(2)O)_(n)]-and KNO_(3)(H_(2)O)_(n)hydrated clusters are systematically investigated atωB97XD/6-311++G(d,p)basis level based on density functional theory(DFT)to understand the micro-hydrated structures of K^(+)and NO_(3)^(-),and the K^(+)-NO_(3)^(-)ion association characteristics in aqueous KNO_(3)solution.Meanwhile,the KNO_(3)solutions in different concentrations are also studied by molecular dynamics(MD)simulation with OPLS-AA all-atom force filed and SPC/E water model.The results showed that the four-,five-,and six-hydrated structures are stable for the first hydration layer of K^(+)in KNO_(3)(H_(2)O)_(n)(n=6,8,10 and 12)hydrated clusters,and the five-hydrated structure is the most stable.The solvent-shared ion pairs are the main form for K^(+)and NO_(3)^(-)in KNO_(3)(H_(2)O)_(n)hydrated clusters.The contact ion pairs(CIP)appear as cluster size decreasing.Meanwhile,MD simulation confirmed that direct contact K^(+)-NO_(3)^(-)ion pairs were formed in concentrated KNO_(3)solutions,and the formation of CIP species had to cross a larger energy barrier with the increase of solution concentration.It could be considered that the hydrated K^(+)and hydrated NO_(3)^(-)are the mainly species for dilute KNO_(3)solutions,the monodentate direct contact ion pair(MCIP)structure gradually appeared with the concentration increasing.In high concentration or supersaturated KNO_(3)solutions,the K^(+)-NO_(3)^(-)ion association is mainly as MCIP and a small amount of bidentate direct contact ion pair.

关 键 词：KNO_(3)溶液 密度泛函理论 分子动力学模拟 微观水合结构 离子缔合 

分 类 号：O642.5[理学—物理化学]