Ortiz de Zárate José M
Facultad de Ciencias Físicas, Universidad Complutense, Plaza de las Ciencias 1, 28040, Madrid, Spain.
Eur Phys J E Soft Matter. 2019 Apr 5;42(4):43. doi: 10.1140/epje/i2019-11803-2.
The definitions of thermodiffusion and Soret coefficients for a binary mixture include a concentration prefactor x(1 - x), when mole fraction x is used, or w(1 - w), when mass fraction w is used. In this paper the physical reasons behind this choice are reviewed, emphasizing that the use of these prefactors makes the thermodiffusion and the Soret coefficients invariant upon changing in the concentration representation, using either mole fraction or mass faction. Then, it is shown how this invariance property can be extended to ternary mixtures by using appropriate concentration prefactors in matrix form. The paper is completed with some considerations about alternative definitions of thermodiffusion coefficients, binary limits of the concentration triangle, selection of the dependent concentration in a ternary mixture, use of molar concentrations and, finally, extension to multi-component mixtures.
对于二元混合物，热扩散系数和索雷特系数的定义中包含一个浓度预因子：当使用摩尔分数(x)时为(x(1 - x))，当使用质量分数(w)时为(w(1 - w))。本文回顾了做出这种选择背后的物理原因，强调使用这些预因子使得热扩散系数和索雷特系数在浓度表示形式（使用摩尔分数或质量分数）发生变化时保持不变。然后，展示了如何通过使用矩阵形式的适当浓度预因子将这种不变性扩展到三元混合物。本文最后对热扩散系数的替代定义、浓度三角形的二元极限、三元混合物中相关浓度的选择、摩尔浓度的使用以及最终扩展到多组分混合物进行了一些讨论。
