物理化学学报 >> 2015, Vol. 31 >> Issue (8): 1461-1467.doi: 10.3866/PKU.WHXB201506013

热力学,动力学和结构化学 上一篇    下一篇

铵根离子在水溶液中的跳跃转动机理

张强1,*(),程程1,张霞1,赵东霞2   

  1. 1 渤海大学化学系,辽宁锦州121000
    2 辽宁师范大学化学系,辽宁大连116029
  • 收稿日期:2015-04-17 发布日期:2015-08-12
  • 通讯作者: 张强 E-mail:zhangqiang@bhu.edu.cn
  • 基金资助:
    教育部留学回国人员科研启动基金(46批);国家自然科学基金(21473083)

Jump Rotational Mechanism of Ammonium Ion in Aqueous Solutions

Qiang. ZHANG1,*(),Cheng. CHENG1,Xia. ZHANG1,Dong-Xia. ZHAO2   

  1. 1 Department of Chemistry, Bohai University, Jinzhou 121000, Liaoning Province, P. R. China
    2 Department of Chemistry, Liaoning Normal University, Dalian 116029, Liaoning Province, P. R. China
  • Received:2015-04-17 Published:2015-08-12
  • Contact: Qiang. ZHANG E-mail:zhangqiang@bhu.edu.cn
  • Supported by:
    the Scientific Research Foundation for Returned Scholars, Ministry of Education of China(46批);NationalNatural Science Foundation of China(21473083)

摘要:

铵根离子的动力学行为与生命体内的生物和化学过程密切相关.依据流体力学理论,由于铵根离子与水分子之间存在多个强氢键,其转动应较慢,但实验结果并非如此,其转动的微观机理尚不清晰.本文分子动力学模拟研究表明,水溶液中铵根离子主要以快速、大角度的跳跃方式进行转动,像水分子一样遵从扩展分子跳跃转动模型.通过微观转动模式的分解和两种转动弛豫时间的比较发现,相对其氢键骨架的扩散转动,跳跃转动对其转动速率贡献更大,并随浓度增大不断强化.与水分子氢键交换方式相比,铵根离子更倾向于在非氢键相连的水分子间发生交换.

关键词: 铵根离子, 跳跃转动, 氢键, 分子动力学模拟, 扩展跳跃模型

Abstract:

The dynamic behavior of the ammonium ion is closely related to the biological and chemical processes of life. A fast rotation of NH4 in aqueous solution has been observed in previous experiments, which is unexpected from hydrodynamic theories because of the multiple strong hydrogen bonds (HBs) between ammonium ion and water. The mechanism behind this rotation is still not well understood. The simulations in this work show that a sudden and large-magnitude angular jump rotation occurs during the hydrogen bond exchange processes of the ammonium ion like water. The rotation of the ammonium ion can be approximately described with the extended jump model, and can be decomposed into two independent contributions: the jump rotation and the diffusive rotation of the HB frame. The rotational mobility of the ammonium ion is determined by fast jump rotation compared with the slow diffusive rotation. In addition, the contribution of the jump rotation increases with increasing NH4 concentration. Compared with water, NH4 prefers to exchange its HB between two water molecules without forming a HB each other.

Key words: Ammonium ion, Jump rotation, Hydrogen bond, Molecular dynamics simulation, Extended jump model

MSC2000: 

  • O641