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