Manifestations of the possible thermodynamic origin of water's anomalies in non-classical vapor nucleation at negative pressures

Abstract

Over the years, various scenarios -- such as the stability-limit conjecture (SLC), two critical point (TCP), critical point-free (CPF), and singularity-free (SF) -- have been proposed to explain the thermodynamic origin of supercooled waters anomalies. However, direct experimental validation is challenging due to the rapid phase transition from metastable water. In this study, we explored whether the phase transition pathways from metastable water provide insight into the thermodynamic origin of these anomalies. Using a classical density functional theory approach with realistic theoretical water models, we examined how different thermodynamic scenarios influence vapor nucleation kinetics at negative pressures. Our findings show significant variations in nucleation kinetics and mechanism during both isobaric and isochoric cooling. In the TCP scenario, the nucleation barrier increases steadily during isobaric cooling, with a slight decrease near the Widom line at lower temperatures (Ts). In contrast, the SF scenario shows a monotonic increase in the nucleation barrier. For the CPF scenario, we observed a non-classical mechanism, such as wetting-mediated nucleation (where the growing vapor nucleus is wetted by the intermediate low-density liquid phase) and the Ostwald step rule at low temperatures. Isochoric cooling pathways also revealed notable differences in T-dependent nucleation barrier trends between the TCP and CPF scenarios. Overall, this study underscores the importance of analyzing phase transition kinetics and mechanism to understand the precise thermodynamic origin of supercooled waters anomalies.