Thermodynamic $R$-diagrams reveal solid-like fluid states
  We evaluate the thermodynamic curvature $R$ for fluid argon, hydrogen, carbon dioxide, and water. For these fluids, $R$ is mostly negative, but we also find significant regimes of positive $R$, which we interpret as indicating solid-like fluid properties. Regimes of positive $R$ are present in all four fluids at very high pressure. Water has, in addition, a narrow slab of positive $R$ in the stable liquid phase near its triple point. Also, water is the only fluid we found having $R$ decrease on cooling into the metastable liquid phase, consistent with a possible second critical point. 
George Ruppeiner, Peter Mausbach, and Helge-Otmar May
cond-mat.stat-mech cond-mat.soft