Polyakov Pavel, Zhang Meimei, Müller-Plathe Florian, Wiegand Simone
Forschungszentrum Jülich GmbH, IFF--Weiche Materie, D-52428 Jülich, Germany.
J Chem Phys. 2007 Jul 7;127(1):014502. doi: 10.1063/1.2746327.
Thermal diffusion forced Rayleigh scattering measurements on binary mixtures of carbon tetrabromide (CBr(4)), tetraethylsilane, and di-tert-butylsilane in carbon tetrachloride (CCl(4)) are reported at different temperatures and concentrations. The Soret coefficient of CBr(4) in CCl(4) is positive and S(T) of both silanes in CCl(4) is negative, which implies that the heavier component always moves to the cold side. This is the expected behavior for unpolar simple molecules. Both silanes have the same mass so the influence of the difference in shape and moment of inertia could be studied. For all three systems, S(T) decreases with decreasing CCl(4) concentration. The results are discussed in the framework of thermodynamic theories and the Hildebrand parameter concept. Additionally, the Soret coefficients for both silaneCCl(4) systems were determined by nonequilibrium molecular-dynamics calculations. The simulations predict the correct direction of the thermophoretic motion and reflect the stronger drive toward the warm side for di-tert-butylsilane compared to the more symmetric tetraethylsilane. The values deviate systematically between 9% and 18% from the experimental values.
报道了在不同温度和浓度下，对四溴化碳（CBr₄）、四乙基硅烷和二叔丁基硅烷在四氯化碳（CCl₄）中的二元混合物进行热扩散强迫瑞利散射测量的结果。CBr₄在CCl₄中的索雷特系数为正，而两种硅烷在CCl₄中的S(T)为负，这意味着较重的组分总是向冷侧移动。这是无极性简单分子的预期行为。两种硅烷质量相同，因此可以研究形状和转动惯量差异的影响。对于所有三个体系，S(T)随CCl₄浓度的降低而减小。在热力学理论和希尔德布兰德参数概念的框架内对结果进行了讨论。此外，通过非平衡分子动力学计算确定了两种硅烷 - CCl₄体系的索雷特系数。模拟预测了热泳运动的正确方向，并且反映出与更对称的四乙基硅烷相比，二叔丁基硅烷向热侧的驱动力更强。这些值与实验值系统地偏差9%至18%。
