We study a model for water with a tunable intramolecular interaction $J_{\sigma },$ using mean-field theory and off-lattice Monte Carlo simulations. For all $J_{\sigma }>~0,$ the model displays a temperature of maximum density. For a finite intramolecular interaction $J_{\sigma }>0,$ our calculations support the presence of a liquid-liquid phase transition with a possible liquid-liquid critical point for water, likely preempted by inevitable freezing. For $J=0,$ the liquid-liquid critical point disappears at $T=0.\mathrm{}$

• Received 11 March 2002

DOI:https://doi.org/10.1103/PhysRevE.67.011103