大学物理 ›› 2022, Vol. 41 ›› Issue (5): 63-.doi: 10.16854/j.cnki.1000-0712.210480

• 大学生园地 • 上一篇    下一篇

静电场中水分子的扩散与液固相变

管星悦,李文飞   

  1. 南京大学 物理学院,江苏 南京210093
  • 出版日期:2022-05-20 发布日期:2022-05-11
  • 通讯作者: 李文飞,E-mail: wfli@nju.edu.cn
  • 作者简介:管星悦(1997—),女,浙江杭州人,南京大学物理学院2016级本科生.
  • 基金资助:
    国家自然科学基金(11974173)资助

Self-diffusion and electrofreezing of bulk water under electric field

GUAN Xing-yue,  LI Wen-fei   

  1. Department of Physics, Nanjing University, Nanjing, Jiangsu 210093, China
  • Online:2022-05-20 Published:2022-05-11

摘要: 扩散与相变是本科阶段基础物理教学的重要内容. 本文以体相水分子系统为例,基于分子动力学模拟,研究静电场环境下水分子的扩散和相变. 在较小电场强度情况下,水分子表现出显著的大角度跳跃转动,且转动频次随电场呈先增加后减小的非单调行为. 这种大角度跳跃转动的反常电场依赖性与水分子扩散系数随电场强度变化的非单调性存在较强相关性.在电场强度较大时,水分子系统发生液固相变,即电致结冰,并观察到了两种冰相沿电场方向的层状混合堆叠结构. 该分子动力学模拟有助于学生从微观层次理解分子扩散与相变等物理现象的分子机制,可作为教学实例培养本科生的科研实践能力. 

关键词: 静电场, 扩散, 液固相变, 水分子, 分子动力学模拟

Abstract: Diffusion and phase transition are important elements of basic physics teaching at the undergraduate level. In this paper, we study the diffusion and phase transition of water molecules under an external uniform electric field based on molecular dynamics simulations for bulk water system. In the case of smaller electric field, water molecules exhibit significant angular jump reorientation motions, and the frequency of the rotation shows a non-monotonic increasing-decreasing behavior with the electric field. This anomalous electric field dependence of angular jump reorientation is strongly correlated with the non-monotonicity of the diffusion coefficient of water molecules with electric field. The liquid-solid phase transition of the bulk water system, i.e., electrofreezing phenomenon, was reproduced at stronger electric fields, and the layered stacking pattern of the two ice phases was observed. The direction of this layered stacking pattern is consistent with the direction of the electric field. The molecular simulations provide new insights into the molecular mechanisms of water diffusion and phase transition at the microscopic level, and can be used as a teaching example for students to develop research interests and research practice skills.

Key words: electrostatic field, diffusion, electrofreezing, water, molecular dynamics