Dense gases, liquids and solids

The fourth course in Statistical Thermodynamics examines dense gases, liquids, and solids. As the density of a gas increases, its behavior begins to be influenced by intermolecular forces. For small deviations from the ideal gas behavior, known as the dense gas limit, the change in properties can be estimated using the concept of a configuration integral, which is a modification of the partition function. This leads to the development of equations of state that are density extensions of the ideal gas limit. Intermolecular potential energy functions are introduced and their effect on the behavior of the PVT is examined. As the density increases, a transition to the liquid state occurs. We examine whether this transition is smooth or abrupt by studying the stability of the thermodynamic system under small perturbations. We then present a brief discussion of the definition of the thermodynamic properties of liquids using the concept of the radial distribution function (RDF) and how this function relates to the thermodynamic properties. Finally, we examine two simple models of crystalline solids.