Dense Gases, Liquids and Solids

Course 4 of Statistical Thermodynamics addresses dense gases, liquids, and solids. As the density of a gas is increased, intermolecular forces begin to affect behavior. For small departures from ideal gas behavior, known as the dense gas limit, one can estimate the change in properties using the concept of a configuration integral, a modification to the partition function. This leads to the development of equations of state that are expansions in density from the ideal gas limit. Inter molecular potential energy functions are introduced and it is explored how they impact P-V-T behavior. As the density is increased, there is a transition to the liquid state. We explore whether this transition is smooth or abrupt by examining the stability of a thermodynamic system to small perturbations. We then present a brief discussion regarding the determination of the thermodynamic properties of liquids using concept of the radial distribution function (RDF), and how the function relates to thermodynamic properties. Finally, we explore two simple models of crystalline solids.

• The Configuration Integral
• As the density of a gas is increased, intermolecular forces begin to affect behavior. For small departures from ideal gas behavior, known as the dense gas limit, one can estimate the change in properties using the concept of a configuration integral, a modification to the partition function. This leads to the development of equations of state that are expansions in density from the ideal gas limit. Inter molecular potential energy functions are introduced and it is explored how they impact P-V-T behavior.
• Thermodynamic Stability
• As the density is increased, there is a transition to the liquid state. We explore whether this transition is smooth or abrupt by examining the stability of a thermodynamic system to small perturbations. We also explore Gibb's phase rule.
• The radial distribution function, thermodynamic properties, and MD simulations of liquid properties
• In this Module we present a brief discussion regarding the determination of the thermodynamic properties of liquids using the concept of the radial distribution function (RDF), and how the function relates to thermodynamic properties. This includes introducing the use of molecular dynamics to obtain the radial distribution function.
• Crystalline Solids
• It turns out that we can use the results of simple statistical thermodynamics to describe the behavior of crystalline solids.