Prediction of transport properties of dense gases and liquids

Abstract

AbstractAn accurate and simple theory of transport properties is developed on the basis of the van der Waals concept of a dense fluid. It is shown that the calculated values for the transport coefficients for the rare gases at temperatures and densities greater than the respective critical ones agree to within about 10% with the experimental results in both absolute value and temperature dependence, without invoking an activation barrier. In this a priori theory, the cross‐section, that is the hard sphere diameter, is determined as a function of temperature from the available equilibrium data, within the framework of the van der Waals theory.Evidence in favor of the van der Waals model and against the activation model has also been found in a study of the free path distribution by molecular dynamics computer calculations. This evidence consists of a monotonic free path distribution without a peak near an intermolecular distance at all densities and temperatures for square‐well molecules. Furthermore, the free path distribution as well as the radial distribution function are nearly temperature independent at a given density. Finally, there were found to be more hard core encounters than soft collisions even at liquid densities and low temperatures.