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Molecular Physics
An International Journal at the Interface Between Chemistry and Physics
Volume 118, 2020 - Issue 9-10: Thermodynamics 2019 Conference
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Thermodynamics 2019 Special Issue

On the validity of the Stokes–Einstein relation for various water force fields

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Article: e1702729 | Received 21 Oct 2019, Accepted 22 Nov 2019, Published online: 16 Dec 2019

Figures & data

Table 1. List of studies for which MD-calculated values for self-diffusivities and shear viscosities are available, along with the corresponding exponents for the fractional Stokes-Einstein relation that are calculated in the current study.

Figure 1. (a) Density plotted as a function of temperature for SPC/E (denoted with triangles) and TIP4P/2005 (denoted with circles) water models. Blue colour denotes values at 1 bar, while red colour at 1,000 bar. Solid lines (for T > 273 K) denote values from NIST [Citation62] while dashed lines (for T < 273 K) experimental values reported in [Citation63]. The dashed-dotted vertical black line indicates the temperature equal to 273.15 K. The inset of the lower-left side is a blow-up of the temperature range 180–380 K. (b) Comparison of densities for TIP4P/2005 calculated in the current study (denoted with circles) and in the work of Abascal and Vega [Citation64] (denoted with crosses).

Figure 1. (a) Density plotted as a function of temperature for SPC/E (denoted with triangles) and TIP4P/2005 (denoted with circles) water models. Blue colour denotes values at 1 bar, while red colour at 1,000 bar. Solid lines (for T > 273 K) denote values from NIST [Citation62] while dashed lines (for T < 273 K) experimental values reported in [Citation63]. The dashed-dotted vertical black line indicates the temperature equal to 273.15 K. The inset of the lower-left side is a blow-up of the temperature range 180–380 K. (b) Comparison of densities for TIP4P/2005 calculated in the current study (denoted with circles) and in the work of Abascal and Vega [Citation64] (denoted with crosses).

Figure 2. Arrhenius plots for: (a) the water shear viscosities, and (b) the water self-diffusion coefficients. MD results from SPC/E water model are denoted with triangles and circles, while MD results from TIP4P/2005 are denoted with crosses and x’s. Blue colour in symbols or lines denotes values at 1 bar, while red colour at 1,000 bar. The dashed-dotted vertical black line indicates temperatures equal to 273.15 K. Uncertainties are reported in the Supplemental Information. In the water shear viscosity plot (a) solid lines denote values from NIST [Citation62], while the dashed black line denotes the experimental measurements by Dehaoui et al. [Citation11]. In the water self-diffusion coefficient plot (b) the dashed lines denote experimental measurements from: Price et al. [Citation9] (1 bar, T < 273 K), Krynicki et al. [Citation8] (1 bar, T > 273 K), Prielmeir et al. [Citation4] (1,000 bar, T < 273 K) and Krynicki et al. [Citation8] (1,000 bar, T > 273 K).

Figure 2. Arrhenius plots for: (a) the water shear viscosities, and (b) the water self-diffusion coefficients. MD results from SPC/E water model are denoted with triangles and circles, while MD results from TIP4P/2005 are denoted with crosses and x’s. Blue colour in symbols or lines denotes values at 1 bar, while red colour at 1,000 bar. The dashed-dotted vertical black line indicates temperatures equal to 273.15 K. Uncertainties are reported in the Supplemental Information. In the water shear viscosity plot (a) solid lines denote values from NIST [Citation62], while the dashed black line denotes the experimental measurements by Dehaoui et al. [Citation11]. In the water self-diffusion coefficient plot (b) the dashed lines denote experimental measurements from: Price et al. [Citation9] (1 bar, T < 273 K), Krynicki et al. [Citation8] (1 bar, T > 273 K), Prielmeir et al. [Citation4] (1,000 bar, T < 273 K) and Krynicki et al. [Citation8] (1,000 bar, T > 273 K).

Figure 3. Self-diffusion coefficients of water as a function of the inverse temperature at 1 bar (blue circles) and 1,000 bar (red triangles) for two water models: (a) SPC/E, and (b) TIP4P/2005. Black diamonds denote the MD results of Moultos et al. [Citation32] for T > 273 K. The dashed lines correspond to correlations of all the MD data of the current study. Colour code of dashed lines. Arrhenius (ARH) law: green line; Vogel–Fulcher–Tamann (VFT) equation: magenta line; Speedy – Angel (SA) power law: cyan line, and Mode Coupling Theory (MCT): black line. The dashed-dotted vertical black line indicates temperatures equal to 273.15 K. Uncertainties are reported in the Supplemental Information.

Figure 3. Self-diffusion coefficients of water as a function of the inverse temperature at 1 bar (blue circles) and 1,000 bar (red triangles) for two water models: (a) SPC/E, and (b) TIP4P/2005. Black diamonds denote the MD results of Moultos et al. [Citation32] for T > 273 K. The dashed lines correspond to correlations of all the MD data of the current study. Colour code of dashed lines. Arrhenius (ARH) law: green line; Vogel–Fulcher–Tamann (VFT) equation: magenta line; Speedy – Angel (SA) power law: cyan line, and Mode Coupling Theory (MCT): black line. The dashed-dotted vertical black line indicates temperatures equal to 273.15 K. Uncertainties are reported in the Supplemental Information.

Table 2. Parameters for the MD self-diffusion coefficient of water calculated using different correlations and % average absolute deviation (% AAD) between experimental data and correlations. The MD data are corrected to account for system size effects.

Figure 4. Comparison of the various calculated fractional exponents, t, with the experimental value for two cases: (a) temperatures below 274 K and (b) temperatures above 274 K. Data sources are the same as in Table . The vertical dashed red lines indicate the corresponding values obtained from the experimental data reported by Dehaoui et al. [Citation11].

Figure 4. Comparison of the various calculated fractional exponents, t, with the experimental value for two cases: (a) temperatures below 274 K and (b) temperatures above 274 K. Data sources are the same as in Table 1. The vertical dashed red lines indicate the corresponding values obtained from the experimental data reported by Dehaoui et al. [Citation11].

Figure 5. Testing of the Stokes-Einstein relation D(T/η) for the SPC/E water model: (a) This work, and (b) Other studies. The symbols denote MD results and the dashed lines are from experimental data (Dehaoui et al. [Citation11]) fitted by the fractional Stokes-Einstein relation D(T/η)s. The dashed-dotted black line indicates the experimental data slope for T > 273.15 K. The dashed black line indicates the experimental data slope for T < 273.15 K. The vertical black dotted line indicates temperatures equal to 273.15 K.

Figure 5. Testing of the Stokes-Einstein relation D∼(T/η) for the SPC/E water model: (a) This work, and (b) Other studies. The symbols denote MD results and the dashed lines are from experimental data (Dehaoui et al. [Citation11]) fitted by the fractional Stokes-Einstein relation D∼(T/η)s. The dashed-dotted black line indicates the experimental data slope for T > 273.15 K. The dashed black line indicates the experimental data slope for T < 273.15 K. The vertical black dotted line indicates temperatures equal to 273.15 K.

Figure 6. Testing of the Stokes-Einstein relation D(T/η) for the TIP4P/2005 water model: (a) This work, and (b) Other studies. The symbols denote MD results and the dashed lines are from experimental data (Dehaoui et al. [Citation11]) fitted by the fractional Stokes-Einstein relation D(T/η)s. The dashed-dotted black line indicates the experimental data slope for T > 273.15 K. The dashed black line indicates the experimental data slope for T < 273.15 K. The vertical black dotted line indicates temperatures equal to 273.15 K.

Figure 6. Testing of the Stokes-Einstein relation D∼(T/η) for the TIP4P/2005 water model: (a) This work, and (b) Other studies. The symbols denote MD results and the dashed lines are from experimental data (Dehaoui et al. [Citation11]) fitted by the fractional Stokes-Einstein relation D∼(T/η)s. The dashed-dotted black line indicates the experimental data slope for T > 273.15 K. The dashed black line indicates the experimental data slope for T < 273.15 K. The vertical black dotted line indicates temperatures equal to 273.15 K.

Figure 7. Testing of the Stokes-Einstein relation D(T/η) for various water models. The symbols denote published MD results and the dashed lines are from experimental data (Dehaoui et al. [Citation11]) fitted by the fractional Stokes-Einstein relation D(T/η)s.

Figure 7. Testing of the Stokes-Einstein relation D∼(T/η) for various water models. The symbols denote published MD results and the dashed lines are from experimental data (Dehaoui et al. [Citation11]) fitted by the fractional Stokes-Einstein relation D∼(T/η)s.