Non-equilibrium thermodynamics for surfaces; square gradient theory
Department of Chemistry, Norwegian University of Science and Technology, 7491 Trondheim, Norway
Revised: 23 April 2013
Published online: 17 June 2013
We present a systematic procedure to describe fluid-fluid interfaces of multi-component systems out of equilibrium in a clear macroscopic context on a basis of non-equilibrium thermodynamics. The macroscopic description uses, as Gibbs did for equilibrium interfaces, excess densities. Comparing it with the local description which is based on the non-equilibrium square gradient theory, we show that two descriptions are consistent. This implies that out of equilibrium one can still use interfacial excess densities as if they are functions only of the local temperature and chemical potentials. This justifies that the surface is a separate thermodynamic system and is in local equilibrium.
© EDP Sciences, Springer-Verlag, 2013