2016/05/19 by John Biddle, Biddle, John W., Rakesh S. Singh +14
Engineering · Materials Science · Physics and Astronomy · #FOS: Physical sciences #Material Dynamics and Properties #Phase Equilibria and Thermodynamics #Statistical Mechanics (cond-mat.stat-mech) #Theoretical and Computational Physics
paper · pdf · doi:10.48550/arxiv.1605.05993
openalex publication_date 2016/05/19 · openalex created_date 2022/10/04 · openalex updated_date 2026/07/28
One of the most promising frameworks for understanding the anomalies of cold\nand especially supercooled water is that of two-structure thermodynamics, in\nwhich water is viewed as a non-ideal mixture of two interconvertible local\nstructures. The non-ideality of this mixture may give rise, at very low\ntemperatures, to a liquid-liquid phase transition (LLPT) and a liquid-liquid\ncritical point (LLCP), at which thermodynamic response functions diverge.\nVarious versions of the "two-structure equation of state" (TSEOS) based on this\nconcept have shown remarkable agreement with both experimental data in real\nwater and simulation results. However, recent experiments probing supercooled\nwater at negative pressures reveal the inadequacy of extrapolations of\nequations of state developed for positive pressures, and have begun to shed\nadditional light on the source of the anomalies of supercooled water. We have\nanalyzed simulation results for the TIP4P/2005 model over a broad range of\npositive and negative pressures from ambient temperature to deep supercooling.\nWe find that by explicitly incorporating a liquid-vapor spinodal into a\ntwo-structure equation of state, we are able to match the simulation data in\nTIP4P/2005 with striking accuracy. In particular, our equation of state\nreproduces the observed lines of minima and maxima in the density, isothermal\ncompressibility, and isobaric heat capacity. Contrary to scenarios in which a\nretracing spinodal accounts for the thermodynamic anomalies of water, we find\nthat the liquid-vapor spinodal in this model continues monotonically to lower\npressures as temperature is decreased, influencing but not giving rise to the\nlocus of density maxima and other thermodynamic anomalies. We explain the\nbehavior of TIP4P/2005 in terms of two phenomena: the competition between two\nlocal structures and a monotonic liquid-vapor spinodal.\n