物理化学学报 >> 2004, Vol. 20 >> Issue (03): 302-305.doi: 10.3866/PKU.WHXB20040317

研究简报 上一篇    下一篇

正十六烷体系凝固过程的分子动力学模拟

殷开梁;徐端钧;夏庆;叶雅静;邬国英;陈正隆   

  1. 浙江大学化学系,杭州 310027;江苏工业学院化工系,常州  213016;
  • 收稿日期:2003-07-18 修回日期:2003-09-24 发布日期:2004-03-15
  • 通讯作者: 殷开梁 E-mail:mat-studio@jpu.edu.cn

Molecular Dynamics Simulation on Solidification Process of n-hexadecane Systems

Yin Kai-Liang;Xu Duan-Jun;Xia Qing;Ye Ya-Jing;Wu Guo-Ying;Chen Cheng-Lung   

  1. Department of Chemistry, Zhejiang University, Hangzhou 310027;Department of Chemical Engineering, Jiangsu Polytechnic University, Changzhou 213016;State Key Laboratory of Solidification Processing, Northwestern Polytechnic University, Xi’an 710072;Department of Chemistry, National Sun Yat-sen University, Kaohsiung, Taiwan 80424
  • Received:2003-07-18 Revised:2003-09-24 Published:2004-03-15
  • Contact: Yin Kai-Liang E-mail:mat-studio@jpu.edu.cn

摘要: 采用分子动力学模拟的方法,根据体系热容和自扩散系数的突变,计算了正十六烷体系以及正十六烷和降凝剂α-辛基萘、α-十二烷基萘及α-十六烷基萘等α-烷基萘混合体系的凝点,凝点降低结果与实验值相一致.用径向分布函数及末端距离分布对凝固温度附近体系的微观结构变化进行了研究.结果表明,凝固过程中正十六烷分子倾向于转变成为全反式的构象,以利于分子间平行有序的排列,这和熵减小的原理相一致.结合正十六烷的构象变化,探讨了烷基萘降凝的机理.

关键词: 分子动力学模拟, 正十六烷, α-烷基萘, 自扩散系数, 凝点, 有序

Abstract: Molecular dynamics(MD) simulation was carried out to investigate the solidification processes of n-hexadecane system and the mixture of n-hexadecane with α-alkyl naphthalene such as octyl, dodecyl and hexadecyl naphthalene. The simulation box contained 10 n-hexadecane molecules and/or one α-alkyl naphthalene. Total 200 ps trajectory for each system was collected to execute the structural, fluctuation and dynamic analysis. The calculated heat capacities of pure n-hexadecane system at 313 and 303 K were consistent with the experimental ones. According to the sharp changes of heat capacities and self-diffusion constants with the simulation temperatures, the solidification point was identified for each system. It was found that the solidification point of n-hexadecane is obviously lowered by mixing with α-alkyl naphthalene, and the calculated solidification points of four systems agreed with the experimental ones. The investigation on the microstructures at temperatures before and after solidification revealed that n-hexadecanes tends to arrange orderly during the solidifying process, which is consistent with the fundamental of entropy-decrease. The reason why α-alkyl naphthalene can lower the solidification point of n-hexadecane was explained as due to the fact that the ring of α-alkyl naphthalene was packed by several n-hexadecane molecules which made the order arrangement of n-hexadecane molecules more difficult.

Key words: Molecular dynamics simulation, n-Hexadecane, α-alkyl naphthalene, Self-diffusion constant, Solidification point, Order