Liquid-State Anomalies and the Stell-Hemmer Core-Softened Potential

We study the liquid anomalies arising from the Stell-Hemmer interaction, using molecular dynamics simulations and approximate 2D solutions. We observe in the liquid phase three types of anomalies: (i) An increase in specific volume upon cooling, (ii) an increase in isothermal compressibility upon cooling, and (iii) an increase in the diffusion coefficient with pressure. We relate the anomalies to the existence of two different local structures in the liquid phase.