Polyakov Pavel, Müller-Plathe Florian, Wiegand Simone
Forschungszentrum Jülich GmbH, IFF-Weiche Materie, D-52428 Jülich, Germany.
J Phys Chem B. 2008 Nov 27;112(47):14999-5004. doi: 10.1021/jp805449j.
We studied the thermal diffusion behavior of mixtures of benzene and heptane isomers by reverse nonequilibrium molecular dynamics. For n-heptane/benzene mixtures, we investigated the concentration dependence of the Soret coefficient. The Soret coefficient for equimolar mixtures of the three heptane isomers 3-methylhexane, 2,3-dimethylpentane, and 2,4-dimethylpentane in benzene has been calculated. Compared to the experimental data, the simulation results show the same trend in dependence of the mole fraction and degree of branching. The negative Soret coefficient indicates the enrichment of alkanes in the warm side. In the case of the heptane isomers in benzene, we could study the influence of the difference in shape and size on the thermal diffusion behavior at constant mass. In the simulation as well as in the experiment, we found that the Soret coefficients become higher with increasing degree of branching. Such behavior cannot be explained only by mass and size effects. The effect of the molecular shape needs to be considered additionally.
我们通过反向非平衡分子动力学研究了苯与庚烷异构体混合物的热扩散行为。对于正庚烷/苯混合物，我们研究了索雷特系数的浓度依赖性。计算了苯中三种庚烷异构体3-甲基己烷、2,3-二甲基戊烷和2,4-二甲基戊烷等摩尔混合物的索雷特系数。与实验数据相比，模拟结果在摩尔分数和支化度依赖性方面显示出相同的趋势。负的索雷特系数表明烷烃在热侧富集。对于苯中的庚烷异构体，我们可以研究形状和尺寸差异对恒定质量下热扩散行为的影响。在模拟和实验中，我们发现索雷特系数随着支化度的增加而升高。这种行为不能仅用质量和尺寸效应来解释。还需要考虑分子形状的影响。
