Langmuir膜相变分子动力学模拟的改进

Improvement on Molecular Dynamics Simulation of Phase Transitions in Langmuir Monolayers

运用分子动力学方法研究了气－液界面单分子膜（Ｌａｎｇｍｕｉｒ膜）的结构和相变特性。模拟中采用了新的头基模型，发现在压膜过程中，膜的结构存在相变。在排列比较疏松时，由于引力作用，分子趋向于聚集成团，出现类似于Ｄｏｍａｉｎ和Ｄｅｆｅｃｔ的结构。脂肪链一般均倾向于相邻的分子，且算得的倾斜角与其它文献的结果不同，分子的倾角随面密度的增大而减小。能量计算表明分子链内无序的主要原因是脂肪链两端二面角的扭曲造成的，膜在压得较紧时较有序。

The structure and phase transitions of stearate Langmuir film are studied using molecular dynamics with a new head group medel.The results show the monolayer experienced two phase transi-tions during comprehension,which may correlate to the gas-liquid and liquid-solid transitions in Lang-muir films . In the case of loose packing, molecules tended to aggregate and defects are obeerved, Themolecular chains tilted to their neighbors with a collective behavior and the tilt angle are different fromthe previous references, The results of energy calculation show that the disorder occuring in molecules is mainly caused by the torsion of the dihedrals at the two ends of molecular chains.