Teaching Theoretical Physical Chemistry: Density Functional Theory and the Taylor Expansion of the van der Waals Free Energy

Abstract

We present a simple demonstration of classical density-functional theory. The starting point is the free energy derived from the van der Waals equation and the familiar gas-liquid phase transition associated with this famous equation. We then construct an approximate free energy by Taylor expansion, illustrating the ideas behind the functional methods used in modern density-functional theory. This presentation also illustrates some of the issues involved in starting a theoretical research project involving undergraduates.