The simplest system where the microscopic physical nature of thermodiffusion can be understood theoretically is a binary mixture. The case of a liquid mixture is considered here, starting from the equilibrium state such as described by thermodynamics. Under a uniform temperature, gradients of composition and/or pressure bring about a non-equilibrium state where local enthalpy is not minimum and/or local entropy is not maximum. The gradients of enthalpy and entropy define a thermodynamic force which is shown to drive composition and pressure diffusions. The thermodynamic force considered in this paper has the physical dimension of a force, it is defined per particle, it is invariant under gauge transformations of enthalpy and entropy and lastly it obeys Newtonʼs third law. Under a non-uniform temperature, it is shown that such a thermodynamic force does not account for thermodiffusion. The thermodiffusive force is of a non-thermodynamic essence. The kinetic-theory account of the transport coefficients is examined in mixtures of long macromolecules with small solvent molecules.
@article{CRMECA_2013__341_4-5_365_0,
author = {\'Eric Bringuier},
title = {Simple ideas about thermodiffusion in a binary liquid mixture},
journal = {Comptes Rendus. M\'ecanique},
pages = {365--371},
publisher = {Elsevier},
volume = {341},
number = {4-5},
year = {2013},
doi = {10.1016/j.crme.2013.01.010},
language = {en},
}
Éric Bringuier. Simple ideas about thermodiffusion in a binary liquid mixture. Comptes Rendus. Mécanique, Volume 341 (2013) no. 4-5, pp. 365-371. doi : 10.1016/j.crme.2013.01.010. https://comptes-rendus.academie-sciences.fr/mecanique/articles/10.1016/j.crme.2013.01.010/
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