User-friendly, theory-based web applet for rapidly predicting structure and thermodynamics of complex fluids

Based on a recently introduced analytical strategy [Hollingshead et al., J. Chem. Phys. 139, 161102 (2013)], we present a web applet that can quickly and semi-quantitatively estimate the equilibrium radial distribution function and related thermodynamic properties of a fluid from knowledge of its pair interaction. We present a detailed description of the applet's features and intended workflow, followed by a description of how the applet can be used to illustrate two (of many possible) concepts of interest for introductory statistical mechanics courses: the transition from ideal gas-like behavior to correlated-liquid behavior with increasing density and the tradeoff between dominant length scales with changing temperature in a system with ramp-shaped repulsions. The latter type of interaction qualitatively captures distinctive thermodynamic properties of liquid water because its energetic bias toward locally open structures mimics that of water's hydrogen-bond network.