Li+的水合结构和近似饱和水合层:基于密度泛函理论的研究

Hydrated Structure and Approximated Complete Hydration Shell of Li+:A Density Functional Theory Investigation

中文关键词:  [Li(H₂O)_n]⁺水合团簇  水合离子  配位数  近似饱和水合层  红外光谱

英文关键词:[Li(H₂O)_n]⁺ hydrated cluster  Hydrated ions  Coordination number  Approximated complete hydration shell  IR spectra 

中文摘要:

      结合密度泛函理论,运用B3LYP/aug-cc-pVDZ方法对[Li(H₂O)_n]⁺(n=1~10)水合团簇的结构进行了研究。研究结果表明,在气相和液相中,四配位结构的[Li(H₂O)_n]⁺水合团簇比其五配位的异构体稳定,即在水溶液中Li⁺易形成四配位的四面体结构。随着同时水分子数的增加,Li-O键长增大,Li⁺上的电荷密度减小。但是当水分子数大于4时,Li-O键长和Li⁺上的电荷密度变化很小。[Li(H₂O)_n]⁺水合团簇中每个水分子的结合能计算结果表明,7个水分子已足以形成Li⁺的近似饱和水合层。另外红外光谱显示[Li(H₂O)_n]⁺水合团簇中O-H伸缩振动随着水分子数的增加发生蓝移,而~3 600 cm-1和~3 500 cm-1处的吸收峰是第二水合层与第一水合层、第三水合层和第二水合层的水分子形成氢键引起的。

英文摘要:

      :The density functional theory with Becke’s three-parameter exchange potential and Lee-Yang-Parr correlation functional (B3LYP) was used to study the structure of [Li(H₂O)_n]⁺ (n=1~10) hydrated clusters.Our calculations show that four-coordinated structure is more stable than its isomer, five-coordinated structure, both in gas and aqueous phases. Namely the Li⁺ tends to form four-coordinated conformer in aqueous solution.The Li-O bond distance increases with the increasing water molecules, while the positive charge on Li⁺ decreases.As n>4, the variation of Li-O bond distance and the positive charge on Li⁺ can be neglected. The binding energy of [Li(H₂O)_n]⁺ hydrated clusters presents that seven water molecules can form an approximated complete hydration shell of Li⁺. In addition, IR spectra of [Li(H₂O)_n]⁺ hydrated clusters reveals that the O-H stretching vibration are blue-shift with the increasing water molecules, and the absorption bands at ~3 600 cm-1and ~3 500 cm-1 can be attributed to the formation of hydrogen bonds between the second and first hydration shell water molecules, and the third and second hydration shell water molecules.