Intermolecular Force Constants from Thermal Diffusion and Other Properties of Gases

Abstract

The thermal diffusion data on argon have been examined on the basis of the Lennard‐Jones 12:6 model by reducing the experimental data through a more appropriate variation of R_T with temperature than has been done hitherto. The value of the force constant ε, thus determined from the observed variation of R_T with temperature, is found to increase slightly with temperature. This variation of ε shows the inadequacy of the model in the entire range of temperatures but gives a good idea of its effective range of usefulness. These values of ε have been utilized to give r₀ from the viscosity and self‐diffusion data. From these the force constants μ and λ have also been evaluated and are likewise found to vary with temperature. These variations of ε, r₀, μ, and λ have been explained theoretically and are shown to be in accord with experimental data on the second virial coefficients of argon. The force constants for O₂, N₂, CH₄, and CO have also been similarly determined and are found to agree with other determinations.