Detailed Molecular Dynamics Simulation of the Structure and Self-Diffusion of Linear and Cyclic n-Alkanes in Melt and Blends
Detailed Molecular Dynamics Simulation of the Structure and Self-Diffusion of Linear and Cyclic n-Alkanes in Melt and Blends
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DOI：
10.1002/mats.201600049
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发表时间：
2017-01-01
影响因子：
1.4
通讯作者：
Mavrantzas, Vlasis G.
中科院分区：
文献类型：
--
作者：
Alatas, Panagiotis V.;Tsalikis, Dimitrios G.;Mavrantzas, Vlasis G.
结果提出的密度，自由体积，自扩散，结构和构象短的线性和环状正构烷烃在自己的熔体和共混物在等碳数从详细的原子分子动力学（MD）模拟等温等压（NPT）统计系综使用显式原子优化的潜力液体模拟（OPLS-AA）力场。与von Meerwall等人（2003年）在早期研究中报告的实验数据一致，环状烷烃的特征是密度较高，扩散速度比同等的直链烷烃慢。它们的构型也受某些构象异构体的支配，这些构象异构体的确切形状取决于环状烷烃的分子长度n。n值越小，这些构象异构体的形状越对称。MD结果支持von Meerwall等人（2003年）的发现，即直链和环状烷烃在其混合物中的总体（单一平均）扩散系数等于相同温度下纯物质扩散系数的重量平均值。模拟结果还提出了两个组件（线性和环状）的平均尺寸，个人的扩散系数，和分子间的C-C对分布函数的分子量和共混物浓度的函数在环状分子。
Results are presented for the density, free volume, self-diffusion, structure, and conformation of short linear and cyclic n-alkanes in their own melt and in blends at equal carbon number from detailed atomistic molecular dynamics (MD) simulations in the isothermal-isobaric (NPT) statistical ensemble using the explicit-atom optimized potentials for liquid simulations (OPLS-AA) force-field. In agreement with experimental data reported in an earlier study by von Meerwall et al. (2003), cyclic alkanes are characterized by higher densities and diffuse more slowly than their equivalent linear alkanes. Their configurations are also dominated by certain conformers whose exact shape depends on the molecular length n of the cyclic alkane. The smaller the value of n the more symmetric the shape of these conformers. The MD results support the findings of von Meerwall et al. (2003) that the overall (single average) diffusion coefficient of linear and cyclic alkanes in their blend is equal to the weight-average of the diffusion coefficients of the neat species at the same temperature. Simulation results are also presented for the average size, individual diffusivities, and intermolecular C-C pair distribution function of the two components (linear and cyclic) as a function of molecular weight and blend concentration in cyclic molecules.