The Free Energy Surface of Supercooled Water

Abstract

We present a detailed analysis of the free energy surface of a well characterized rigid model for water in supercooled states. We propose a functional form for the liquid free energy, supported by recent theoretical predictions [Y. Rosenfeld and P. Tarazona, Mol. Phys. {\bf 95}, 141 (1998)], and use it to locate the position of a liquid-liquid critical point at $T_{C^{\prime }}=130\pm 5$~K, $P_{C^{\prime }}=290\pm 30$MPa, and ${\rho }_{C^{\prime }}=1.10\pm 0.03$~g/cm${}^3$. The observation of the critical point strengthens the possibility that SPC/E water may undergo a liquid-liquid phase transition. Finally, we discuss the possibility that the approach to the liquid-liquid critical point could be pre-empted by the glass transition.