The role of molecular interactions in the change of sign of the Soret coefficientB. Rousseau1, C. Nieto-Draghi2 and J. Bonet Avalos2
1 Laboratoire de Chimie Physique, Bâtiment 350, Université Paris Sud 91405 Orsay Cedex, France
2 Departament d'Enginyeria Química, ETSEQ, Universitat Rovira i Virgili Avda. dels Països Catalans 26, 43007 Tarragona, Spain
(Received 20 February 2004; accepted in final form 6 July 2004)
The change of sign with composition in aqueous mixtures of associating fluids is analyzed by means of molecular-dynamics simulations. The results obtained are in quantitative agreement with the experimental data in water-ethanol and water-methanol solutions, which exhibit the mentioned change of sign. A subsequent theoretical analysis is addressed to establish a relationship between the dependence of the Soret coefficient with composition with the existence of large inter-species interactions. Although the change of sign of the Soret coefficient with composition is not only due to the so-called chemical contribution analyzed here, we discuss the role that these interactions play in such a change of sign.
66.10.Cb - Diffusion and thermal diffusion.
05.70.Ln - Nonequilibrium and irreversible thermodynamics.
05.60.-k - Transport processes.
© EDP Sciences 2004