9 Microscopic and Macroscopic Stress with Gravitational and Rotational

and James F. Lutsko Physics Department CP 231 Université Libre de Bruxelles Blvd. du Triomphe, 1050 Brussels, Belgium Abstract Many recent papers have questioned Irving and Kirkwood’s atomistic expression for stress. In Irving and Kirkwood’s approach both interatomic forces and atomic velocities contribute to stress. It is the velocity-dependent part that has been disputed. To help clarify this situation we investigate (i) a fluid in a gravitational field and (ii) a steadily rotating solid. For both problems we choose conditions where the two stress contributions, potential and kinetic, are significant. The analytic force-balance solutions of both these problems agree very well with a smooth-particle interpretation of the atomistic Irving-Kirkwood stress tensor.