Long-range structure in simulations of glassy water exhibits evidence of metastable criticality

Supercooled and glassy water exhibits many interesting and unusual properties; two examples include polyamorphism (multiple glassy states) and the theorized liquid-liquid critical point (LLCP) and associated liquid-liquid transition under metastable supercooled conditions. Despite the natural analogy between the low-density and high-density forms of amorphous ice and the corresponding forms of supercooled liquid water, the exact relationship between the amorphous ices and the supercooled liquid is incompletely understood. We performed molecular dynamics simulations of isobaric glass formation at various pressures using the TIP4P/2005 and mW water models, as well as the Kob-Andersen mixture. We observed that systems that possess an LLCP (TIP4P/2005) exhibit increased long-range density inhomogeneities in glasses formed near the liquid-liquid critical pressure, which persist even as the system is cooled to low temperatures. This behavior is absent at pressures far away from the critical pressure, as well as in systems that do not exhibit an LLCP (mW, Kob-Andersen). These findings suggest a possible structural metric to detect whether a system exhibits an LLCP, and shed additional light on the relationship between polyamorphism and metastable criticality in water.