质子水合结构的振动态密度分析

使用基于多态经验价键模型的分子动力学模拟, 对水溶液中质子的水合结构及其在质子传递过程中的动力学过程进行了研究. 在价键模型的方法下, 质子的水合结构主要以H₉O₄⁺(Eigen)以及过渡态的H₅O₂⁺(Zundel)结构形态存在, 且在这两种结构中以Eigen的形态表现明显. 通过对质子传递过程中不同水合结构的态密度频谱分析, 发现一个在2000~3000 cm^-1范围内的明显连续的宽吸收谱带, 主要归因于Eigen结构的贡献, 这些特征峰的出现与水合氢离子第一溶剂化层内的强氢键作用密切相关. 对于Zundel的结构, 在1760 cm^-1处出现一个较为明显的肩峰, 归属为质子传递模式的特征振动. 通过对质子水合结构态密度频谱的分析, 可望增强对于稀酸溶液红外光谱中的连续宽吸收带以及质子传递的微观动力学过程的理解.

Vibrational Density of States Analysis of Proton Hydration Structure

Proton transfer（PT） is a very important basic reaction process in chemical reactions. It is important for understanding the dynamic process of biology and the development of proton fuel cells. In the work， the hydration structure of proton and the dynamic response of the hydration structure involved in the PT process in aqueous solution were studied in detail by the molecular dynamics simulation using multistate empirical valence bond（MS-EVB） model. Based on the theoretical framework of MS-EVB model， the proton hydration structure mainly exists in the form of H₉O₄⁺（Eigen） or the intermediate of H₅O₂⁺（Zundel）， and the Eigen is do-minant in these two structures. Density of state（DOS） spectra of different hydration structures in PT process show continuous broad absorption band in the range of 2000―3000 cm^-1， which is mainly attributed to the Eigen contribution because there are no obvious characteristic peaks for a Zundel structure at the above frequency. The characteristic peak is closely related to the strong hydrogen bonding in the first hydration shell of hydronium ions in Eigen structure. Moreover， for Zundel structure， a relatively obvious shoulder appears at 1760 cm^-1， which is attributed to the characteristic of PT mode， in agreement with previous study. Through the analysis of DOS spectrum associated with PT， we hope to improve the understanding on the continuous broad absorption band in the infrared spectrum of the dilute acid solution， and the microscopic dynamical characte-ristic of PT in the aqueous solution.