Statistical thermodynamics of material transport in non-isothermal binary systems

Institute of Biochemical Physics RAS - 119334 Moscow, Kosygin Street 4, Russia

^a sem@triniti.ru

Received: 24 April 2011
Accepted: 15 February 2012

Abstract

The material transport equations derived by non-equilibrium thermodynamics are used to describe the material transport in binary non-isothermal molecular systems. The chemical potentials of the components used in the equations are calculated using statistical mechanics. As the material transport equations contain chemical potentials at constant pressure, the local pressure distribution necessary in calculations is obtained using the condition of the local thermodynamic equilibrium around the selected molecular particle. The Laplace contribution to the local pressure distribution within the layer of the liquid around the particle is accounted. The calculations yield the results equivalent to previous approaches and add new terms to the Soret coefficient, which are related to the difference in the translational and rotational thermal motion between the molecules. The kinetic contribution to thermodiffusion explains the isotope thermodiffusion effect, the role of the molecular symmetry, and the sign change in thermodiffusion observed in binary systems. The proposed theory describes thermodiffusion in binary molecular systems with a limited miscibility.