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Prediction of physical properties of water under extremely supercritical conditions: A molecular dynamics study
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10.1063/1.4798222
/content/aip/journal/jcp/138/13/10.1063/1.4798222
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/13/10.1063/1.4798222

Figures

Image of FIG. 1.
FIG. 1.

Developed five-site water model. The x axis is perpendicular to the molecular plane, which is represented by the yz plane. The permanent and induced point charges are located on two hydrogen atoms and on two lone pairs of the oxygen atom. The positions of the lone pairs are fixed along the x axis (r OLP = 0.2 Å). The total charge of the H2O molecule is neutralized.

Image of FIG. 2.
FIG. 2.

Comparison experimental and MD results for water density (T < 1000 K, p < 1000 MPa) and the prediction of the densities at high temperature and pressure up to T ≤ 2000 K and p ≤ 2000 MPa. The lines indicate the experimental results for IAPWS95 11 and sound velocity measurements. 49

Image of FIG. 3.
FIG. 3.

Radial distribution functions of (a) oxygen–oxygen (g OO), (b) oxygen–hydrogen (g OH), and (c) hydrogen–hydrogen sites (g HH) at T = 573 K, p = 280 MPa, and T = 673 K, p = 340 MPa. MD results (solid lines) are compared with experimental neutron diffraction data (dashed lines). 50 High-temperature and high-pressure data are shifted for comparison on the same graph.

Image of FIG. 4.
FIG. 4.

(a) Radial distribution functions of oxygen–oxygen sites g OO at T = 673 K and p = 100, 340, 870, and 1190 MPa. MD results (solid lines) are compared with experimental data (dashed lines) for neutron diffraction 50 at 340 MPa and x-ray diffraction data 51 at 870 and 1190 MPa. The pressures for the x-ray diffraction data were calculated by conversion of the density using the IAPWS95 data. 11 High-pressure data are shifted for comparison on the same graph. (b) Running coordination number (rcn) of oxygen–oxygen sites.

Image of FIG. 5.
FIG. 5.

(a) Cumulative averages of calculated static dielectric constant of water at p = 2000 MPa and various temperatures. (b) Calculated static dielectric constant of water at various pressures and temperatures. Experimental values 56 are shown as bold lines for comparison. Solid thin lines in (b) indicate fitting curves to the MD results, Eq. (20) .

Image of FIG. 6.
FIG. 6.

Distributions of absolute values of molecular dipole moment at p = (a) 340 MPa, (b) 800 MPa, (c) 1500 MPa, and (d) 2000 MPa. Arrows indicate changes in the distributions with increasing temperature.

Image of FIG. 7.
FIG. 7.

Mean and standard deviation of dipole moment of H2O calculated by fitting a Gaussian probability density to the distribution of the dipole moment shown in Fig. 6 . Numbers indicate the temperature (K).

Image of FIG. 8.
FIG. 8.

(a) Mean intramolecular O-H distances r OH, (b) HOH angles, (c) increased percentage of the |r D| (= |r OH1 + r OH2|), and (d) the contribution of the flexibility of the water molecules into the induced dipole moments. The symbols are the same as those in Fig. 2 . (e) Distribution of intramolecular geometry among r OH and HOH angle at T = 673 K and p = 340 MPa.

Image of FIG. 9.
FIG. 9.

Rotational correlation functions (a) C 2 y (t) and (b) C 1 z (t) at p = 2000 MPa and the long-term exponential decay times (c) τ 2 y and (d) τ 1 z .

Image of FIG. 10.
FIG. 10.

(a) Self-diffusion coefficients and (b) viscosity of water calculated by MD simulations. Bold lines are the experimentally obtained self-diffusion coefficients 62 and viscosity. 65

Image of FIG. 11.
FIG. 11.

A comparison of the density at T = 673 K among water models and experiments. 11,49

Image of FIG. 12.
FIG. 12.

Radial distribution functions of (a) oxygen–oxygen (g OO), (b) oxygen–hydrogen (g OH), and (c) hydrogen–hydrogen sites (g HH) at T = 673 K and p = 340 MPa. MD results using various water models are compared with experimental neutron diffraction data. 50

Image of FIG. 13.
FIG. 13.

Static dielectric constants calculated at T = 673 K using various water models and the experimental data. 56

Tables

Generic image for table
Table I.

Potential parameters of the FIPC model.

Generic image for table
Table II.

Parameters relating to the polarization.

Generic image for table
Table III.

Comparison of static dielectric constant of water calculated in this study and experimental values. Experimental values at p = 130, 140, and 340 MPa are derived from interpolation of experimental data. 56

Generic image for table
Table IV.

Static dielectric constants calculated using Eq. (20) .

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/content/aip/journal/jcp/138/13/10.1063/1.4798222
2013-04-02
2014-04-19
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Prediction of physical properties of water under extremely supercritical conditions: A molecular dynamics study
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/13/10.1063/1.4798222
10.1063/1.4798222
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