Statistical thermodynamic expression for the Soret coefficient
Institute of Biochemical Physics, RAS - Kosygin Street 4, 119334 Moscow, Russia
Corresponding author: firstname.lastname@example.org
Accepted: 28 May 2010
The thermodynamic Soret coefficient for diluted mixtures expressed through the temperature derivative of the particle chemical potential at constant pressure is calculated using statistical mechanics. The local pressure distribution is obtained using the condition of the local thermodynamic equilibrium around an isolated particle. The Laplace contribution to the local pressure distribution within the layer of the liquid around the particle is accounted. The calculations yield results equivalent to the hydrodynamic approach and add a new kinetic term to the Soret coefficient. This term is related to the difference in the thermal velocities between the particles with different mass. The kinetic contribution to thermodiffusion explains the isotope thermodiffusion effect observed in molecular systems. The theory describes most of the experimental data on thermodiffusion of the isolated molecular and colloid particles placed in non-electrolyte liquids.
PACS: 65.20.-w – Thermal properties of liquids / 66.10.C- – Diffusion and thermal diffusion / 66.10.cd – Thermal diffusion and diffusive energy transport
© EPLA, 2010