Density ρ, isobaric heat capacity C P , isothermal compressibility κ T , and thermal expansivity α P computed from the mW model (points) compared with the results (curves) of the two-state approach for an athermal solution [Eq. (13) ]. The isobar pressures are given in the density diagram; pressures and corresponding isobar colors are the same in the four panels.
Fraction x of molecules in the low-density state. Solid curves: fraction x for the (a) two-state equation of state, Eq. (13) ; (b) two-state equation accounting for hexamer clustering, Eq. (16) with N = 6. Dashed curves: fraction x obtained from simulations of mW water, calculated from the fraction of four-coordinated molecules f 4 as , to account for fractions and of four-coordinated molecules in the low- and high-temperature liquid, respectively. The inflection points on the curves are marked with circles (two-state equation) and squares (mW model). The data were collected by linearly quenching the temperature of the simulations at a rate of 10 K/ns. The data below the inflection point do not correspond to equilibrium states.
Pressure–temperature diagram. Circles: location of the computed property data of the mW model. Solid line: line at which ln K = 0 and the low-density fraction x = 1/2 for the two-state equation. Squares: location of inflection points of the low-density fraction x for the mW model (see Fig. 2 ). Dotted line: stability-limit temperature from the fit of the weak crystallization model to the mW data, Eq. (26) . The dashed curve is a fit to the melting temperature of mW ice (uncertainty about ±3 K), obtained from free energy calculations as described in Ref. 20 .
Enthalpy ΔH (a) and entropy ΔS (b) of liquid mW water with respect to ice at 0.1 MPa (black curves, from Moore and Molinero 19 ) and their fits (dashed red curves) according to Eqs. (18) and (19) , respectively. Both ΔH and ΔS are computed at a cooling rate of 10 K/ns, which prevents crystallization, so that the values below 200 K do not correspond to an equilibrium state. The circle signals K. These results support the modeling of mW water as an athermal mixture of two states.
Heat capacity of mW water in equilibrium (circles) and on hyperquenching at 10 K/ns (black curve, computations by Moore and Molinero 19 ). The values below 200 K do not correspond to an equilibrium state. The dashed curve is the prediction of the two-state equation with hexamer clusters.
Fluctuation-renormalized distance to the stability-limit temperature Δ, given by Eq. (21) , as a function of the mean-field distance to the stability limit Δ0, for two values of β (solid curves). The dashed line corresponds to Δ = Δ0 and is shown as a reference.
Density ρ, isobaric heat capacity C P , isothermal compressibility κ T , and thermal expansivity α P computed from the mW model (points) compared with the fit to power laws given by weak crystallization theory (curves). The isobar pressures are given in the density diagram; pressures and corresponding isobar colors are the same in the four panels.
Fluctuations of the crystallization order parameter from weak crystallization theory (i.e., short-wavelength density fluctuations) in arbitrary units as a function of temperature, fit with Eq. (28) (curve).
Article metrics loading...
Full text loading...