Phase diagram of the ST2 model of water

Abstract

We evaluate the free energy of the fluid and crystal phases for the ST2 potential [F.H. Stillinger and A. Rahman, J. Chem. Phys. 60, 1545 (1974)] with reaction field corrections for the long-range interactions. We estimate the phase coexistence boundaries in the temperature-pressure plane, as well as the gas-liquid critical point and gas-liquid coexistence conditions. Our study frames the location of the previously identified liquid-liquid critical point relative to the crystalline phase boundaries, and opens the way for exploring crystal nucleation in a model where the metastable liquid-liquid critical point is computationally accessible.

Pattern of property extrema in supercooled and stretched water models and a new correlation for predicting the stability limit of the liquid state

“…We present a rescaling of the thermodynamic property extrema of previously published and new simulation results for three commonly used molecular models of water (ST2, 38,57,60 TIP4P/2005, 44,58 and TIP5P). The rescaling procedure results in a satisfactory near-collapse of the property extrema loci for these three models.…”

“…For the analysis of property extrema in molecular water models in the supercooled and stretched regions, we use molecular dynamics simulations of the ST2 38,57,60 and TIP4P/2005 water models 44,58 and report new data for the TIP5P model. The information on the property extrema in the ST2 and TIP4P/2005 models as well as for the previously unpublished TIP5P model is presented in the supplementary material.…”

“…In addition to the molecular water models, we also consider preliminary results for a two-structure equation of state (TSEOS) fit to experimental data for real metastable and stretched water. 59 Figure 2 depicts the extrema of density, isothermal compressibility (computed along isobars), and isobaric heat capacity (computed along isotherms) for three molecular water models that exhibit a liquid-liquid phase transition terminating at a critical point, namely, ST2, 38,57,60 TIP4P/2005, 44,58 and TIP5P (supplementary material), and for real water obtained from the TSEOS fit to existing experimental data. 59 The stability limit of the liquid with respect to the vapor gives the lower limit of the phase diagram of liquid water.…”

“…Computer simulations, on the other hand, have shown that some molecular models of water exhibit liquid-liquid separation at deeply supercooled conditions. 22,[38][39][40][41][42][43][44][45][46][47][48] In tetrahedral systems, regardless of the existence or non-existence of the liquid-liquid separation (e.g., mW, [49][50][51] mTIP4P, 50 ST2, 52 The Journal of Chemical Physics ARTICLE scitation.org/journal/jcp TIP4P/2005, 53 TIP5P, 54 silicon, 30,31,55 silica, 32,33 and germanium 56 ), there is an underlying characteristic pattern of extrema lines for thermodynamic properties. The most wellknown is the line of density extrema, whose existence suggests a competition between low-density and high-density structures in the same liquid.…”

Glass polymorphism and liquid–liquid phase transition in aqueous solutions: experiments and computer simulations

“…There, also the HDL -LDL and LDL -HDL spinodal lines are shown. Besides ST2 water which exhibits an unambiguous LLCP/LLPT, 29,[41][42][43][44][45][46] indications for an LLCP were also reported for other rigid water models. [47][48][49][50] The estimated LLCP loci in different models are summarized in Table 1.…”