Fluctuation theory for transport properties in multicomponent mixtures: thermodiffusion and heat conductivity

The theory of transport properties in multicomponent gas and liquid mixtures, which was previously developed for diffusion coefficients, is extended onto thermodiffusion coefficients and heat conductivities. The derivation of the expressions for transport properties is based on the general statistical theory of fluctuations around an equilibrium state. The Onsager matrix of phenomenological coefficients is expressed in terms of the penetration lengths, including the newly introduced penetration length for the energy transfer. As an example, this penetration length is found from the known value of the heat conductivity coefficient for ideal gas.