On an Approximate Theory of Transport in Dense Media

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Abstract
A new approximate theory of transport is presented which starts from the general statistical mechanical theory of heat flux and the stress tensor and uses three principal approximations. These are (a) the expansion of the gradient of the pair interaction potential between molecules at time t+s about the gradient at time t and the neglect of all terms higher than the second, (b) the use of a local equilibrium distribution function in pair‐space, and (c) the approximation of the pair diffusion tensor as the direct sum of singlet diffusion tensors. The intermolecular force contributions to the shear viscosity, bulk viscosity, and thermal conductivity are related to equilibrium properties of the fluid and, respectively, to other coefficients of the set of transport coefficients. Absolute calculations for liquid argon are within a factor of two of experiment. A semiempirical calculation suggested by the theory and using the observed diffusion coefficient is in exact agreement with experiment. The validity of the three approximations is discussed.