The entropy of a single large finite system undergoing both heat and work transfer

Abstract

Computing the entropy of a system from a single trajectory is discussed when the energy exchange with the environment includes both mechanical and thermal terms. The physical example chosen as an illustration is a cluster of atoms impacting a hard surface. Each atom of the cluster interacts with the smooth surface by a momentum transfer using the hard cube model [E. K. Grimmelmann, J. C. Tully and M. J. Cardillo, J. Chem. Phys. 72, 1039 (1980)]. Because of the thermal motion of the surface atoms the atoms of the cluster rebound from the surface with a (random) thermal component to their momentum. The change in the internal energy of the cluster has therefore both a mechanical, work, term and a heat transfer and the heat term contributes to the change in entropy of the cluster but the major contribution is the loss of potentially available work.

Acknowledgements

This work was supported by the US Air Force Office of Scientific Research. AG is a Clore Foundation Fellow.