Pinpointing the Liquid-Liquid Critical Point Location in Supercooled Water
The fascinating hypothesis that supercooled water may segregate into two distinct liquid phases, each with unique structures and densities, was first posited in a seminal study by Poole, Sciortino, Essman and Stanley in 1992. This idea, initially based on numerical analyses with a water-like empirical potential, challenged conventional understanding of water’s phase behavior at the time and has since intrigued the scientific community. Over the past three decades, advancements in computational modeling – particularly through the advent of data-driven many-body potentials rigorously derived from “first principles” and augmented by the efficiency of neural networks – have significantly enhanced the accuracy of molecular simulations, enabling the exploration of the phase behavior of water with unprecedented realism. This study leverages these computational advances to probe the liquid-liquid transition in supercooled water. For the first time, microsecond-long simulations with chemical accuracy, conducted over several years, provide compelling evidence that water indeed exists in two discernibly distinct liquid states at low temperature and high pressure. By pinpointing a realistic estimate for the location of the liquid-liquid critical point, our study not only advances current understanding of water’s anomalous behavior but also establishes a basis for experimental validation.
Authors: Francesco Sciortino, Yaoguang Zhai, Sigbjørn L. Bore, Francesco Paesani