The metastable liquid-liquid phase transition: from water to colloids and liquid metals

The possibility of a liquid-liquid (LL) phase transition has been proposed as an interpretation of the anomalous behavior of liquids such as water, whose isobaric density has a maximum for decreasing temperature. By using theoretical models and numerical simulations, we show (i) that this property for molecular liquids implies the existence of a LL critical point, (ii) that the existence of a LL critical point does not imply the anomalous density behavior in systems whose effective potential resembles an isotropic soft-core attractive potential, such as protein solutions, colloids, star-polymers and, to some extent, liquid metals.