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利用分子力学和分子动力学计算工具,对钠离子的各种水合结构及能量进行了分子力学和动力学的计算,以此研究水合钠离子所起的结构生成剂的作用。用Monte Carlo Docking方法对各种结构的水合钠离子在MFI分子筛微孔结构内的附着行为模拟计算。结果表明,配位数为偶数时水合阳离子的结构较为合理,这种合理性体现在当配位数为偶数时,Na_-~+nH_2O体系中金属离子的位置与氧原子的位置呈现对称结构,Na_-~+4H_2O和Na_-~+6H_2O是相对比较合适的结构;对于钠离子,配位数为4和6,当配位数大于6时,体系将自动转为6配位的情况;钠离子明显具有对周围的水分子结构进行重新排列的作用;钠离子的配位水分子数为4个或6个,而4配位结构是水合钠离子的主要存在方式之一;在MFI结构分子筛的合成中起模板剂作用的应该是Na_+~+4H_2O结构;计算结果对分子筛合成研究中水合离子的结构生成和结构破坏具有重要的意义。
Molecular mechanics and molecular dynamics calculation tools were used to calculate the molecular hydraulics and kinetics of various hydrated structures and energies of sodium ions to study the role of structural generants of hydration of sodium ions. Monte Carlo Docking method was used to simulate the attachment of various hydrated sodium ions in the microporous structure of MFI molecular sieve. The results show that the structure of hydrated cation is more reasonable when the coordination number is even number. This rationality is reflected in that the position of the metal ion in the Na_- ~ + nH_2O system is symmetrical with that of the oxygen atom when the number of coordination is even, Na_- ~ + 4H_2O and Na_ ~ ~ + 6H_2O are relatively suitable structures; for sodium ions, the coordination numbers are 4 and 6, and when the coordination number is greater than 6, the system will automatically switch to 6-coordinate; sodium The ions obviously have the function of rearrangement of the surrounding water molecules. The number of coordinated water molecules of sodium ions is 4 or 6, and the 4 coordination structure is one of the main ways of existence of hydrated sodium ions. In MFI molecular sieves The structure of Na_ + ~ + 4H_2O should be Na_ + ~ + 4H_2O. The calculated results are of great significance to the structural formation and structural destruction of hydrated ions in the synthesis of molecular sieves.