Molecular origin of thermal diffusion in benzene plus cyclohexane mixtures- art. no. 055901

The isotope effect in thermal diffusion (Soret effect) of benzene + cyclohe xane mixtures has been investigated by a holographic grating technique. The Soret coefficient can be split into additive contributions. One contributi on. the isotope effect, stems from the differences of both mass and moment of inertia, and is independent of composition. An additional "chemical" con tribution depends on concentration and even changes its sign at a benzene m ole fraction X-benz approximate to 0.7. The mass effect is in agreement wit h molecular dynamics calculations: the heavier component migrates to the co ld side.