物理化学学报 >> 2014, Vol. 30 >> Issue (7): 1208-1214.doi: 10.3866/PKU.WHXB201405095

热力学,动力学和结构化学 上一篇    下一篇

均匀电场对冰晶结构及生长的影响

张相雄, 陈民   

  1. 清华大学工程力学系, 北京 100084
  • 收稿日期:2014-03-14 修回日期:2014-05-08 发布日期:2014-06-30
  • 通讯作者: 陈民 E-mail:mchen@tsinghua.edu.cn
  • 基金资助:

    国家自然科学基金(51321002,50876049)资助项目

Influence of Homogeneous Electric Field on the Structure and Growth of Ice

ZHANG Xiang-Xiong, CHEN Min   

  1. Department of Engineering Mechanics, Tsinghua University, Beijing 100084, P. R. China
  • Received:2014-03-14 Revised:2014-05-08 Published:2014-06-30
  • Contact: CHEN Min E-mail:mchen@tsinghua.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (51321002, 50876049).

摘要:

采用分子动力学模拟方法研究了强度为4.0-40.0 V·nm-1的均匀电场对过冷水冰晶结构和冰晶生长速率的影响. 文中通过CHILL 算法来识别不同的冰相结构,通过拟合Avrami 公式来得到冰晶生长所需的特征时间. 结果表明,在所施加的电场强度范围内生成的冰相以立方冰为主. 随着电场强度的增加,形成的立方冰的变形程度逐渐增大,冰晶的密度从0.98 g·cm-3 增加到1.08 g·cm-3,同时冰晶生长的特征时间从5.153 ns 减小到0.254 ns,冰晶生长的速率逐渐增长. 对水分子的动力学分析表明,冰晶生长速率增加的部分原因是电场能够促进水分子运动到形成冰晶所需要的取向. 此外,对冰相分子形成过程的分析表明缺陷冰分子在冰晶的生长过程中扮演着中间态的角色. 随电场强度的增加,由缺陷冰转变为立方冰的比例增长的速率逐渐提高.

关键词: 分子动力学模拟, 均匀电场, 冰晶结构, 冰晶生长速率, 缺陷冰分子

Abstract:

Homogeneous crystallization of supercooled water under electric field with strength ranging from 4.0 to 40.0 V·nm-1 was investigated by using molecular simulation technique. The liquid-solid transition was successfully obtained based on ice component analysis using the CHILL algorithm. The analysis suggested that the produced crystalline was cubic ice dominant. The influence of the field strength on the structure and the growth rate of the ice was studied. The results revealed that the presence of an electric field drove the system to crystallize rapidly into dense and distorted cubic ice. The density of the crystals increased as a function of the field strength, from 0.98 to 1.08 g·cm-3. The growth rate of the ice nucleus increased along with the field strength according to the characteristic time derived from the Avrami equation which ranged from 0.254 to 5.513 ns. This type of acceleration can be partially attributed to the enhancement of the rotational dynamics of the water molecules. Moreover, by monitoring the formation history of the cubic ice, we found that the defective ice acted as a transition state linking the liquid water and the cubic ice.

Key words: Molecular dynamics simulation, Homogeneous electric field, Ice crystal structure, Growth rate of ice crystal, Defective ice molecule

MSC2000: 

  • O643