Contribution to the Friction Coefficient from Time Correlations between Hard and Soft Molecular Interactions

Abstract

The contribution to the friction coefficient arising from correlations between hard and soft forces is evaluated using the linear‐trajectory approximation. This contribution, previously neglected in the theories of Helfand and Rice and Allnatt, is found to be of the same order of magnitude as the hard‐core contribution, which, itself, is important for much of the liquid range of temperature and density.