Diffusion, viscosity, and Stokes-Einstein relation in dense supercritical methane

Khrapak, S. A.

doi:10.1016/j.molliq.2022.118840

Cited by 17 publications

(6 citation statements)

References 28 publications

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“…[21] and the applicability of the SE relation has been confirmed. A few recent examples confirming the applicability of SE relation to real liquids include liquid iron at conditions of planetary cores [22], dense supercritical methane (at least for the most state points investigated) [23,24], silicon melt at high temperatures [25], and liquid water modelled by the TIP4P/Ice model [26,27] (which was specifically designed to deal with water near the fluid-solid phase transition and solid-phase properties [28]).…”

Section: Methodsmentioning

confidence: 95%

Correlations between the Shear Viscosity and Thermal Conductivity Coefficients of Dense Simple Liquids

Khrapak

2021

Jetp Lett.

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A practical correction formula relating the self-diffusion coefficient of dense liquids from molecular dynamics simulations with periodic boundary conditions to the self-diffusion coefficient in the thermodynamic limit is discussed. This formula applies to pure dense fluids and has a very simple form D = D0(1 − γN −1/3 ), where D0 is the self-diffusion coefficient in the thermodynamic limit and N is the number of particles in the simulation. The numerical factor γ depends on the geometry of the simulation cell. Remarkably, γ ≃ 1.0 for the most popular cubic geometry. The success of this formula is supported by results from MD simulations, including very recent simulations with a "magic" simulation geometry.

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Section: Methodsmentioning

confidence: 95%

Correlations between the Shear Viscosity and Thermal Conductivity Coefficients of Dense Simple Liquids

Khrapak

2021

Jetp Lett.

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“…A few recent examples confirming applicability of SE relation in the form of Eq. ( 2) to real liquid substances include liquid iron at conditions of planetary cores [19], dense supercritical methane (at least for the most state points investigated) [20,21], and silicon melt at high temperatures [22]. Several important non-spherical molecular liquids have been examined using numerical simulations in Ref.…”

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confidence: 99%

Stokes–Einstein relation without hydrodynamic diameter in the TIP4P/Ice water model

Khrapak

2023

The Journal of Chemical Physics

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“…Costigliola et al have recently shown that for a Lennard-Jones liquid for low temperatures and high densities, indeed, a value of 0.146 is asymptotically approached, while at large temperatures with α SE ≫ 1/(2π), a breakdown of the Stokes–Einstein relation is observed . The value of α SE ≈ 0.15 for these conditions has recently been confirmed from experimental data for dense supercritical methane . The value of α SE ≈ 0.15 was also reported from an analysis of simulations of TIP4P/ice water by Khrapak and Khrapak, which is in perfect agreement with our results for the TIP4P/2005 model.…”

Section: Resultsmentioning

confidence: 52%

“…Note that the two ethers exhibit considerably larger values than the two other components, which are capable of forming hydrogen bonds. This behavior is perhaps even better reflected by the dimensionless “Stokes–Einstein parameter” − α SE = D 0 η s X k B T = 1 6 π · s normalX R hyd given in Table . The hydrodynamic theory for macroscopic spheres gives α SE ≈ 1/( c π) ranging from 0.106 ( c = 3) to 0.159 ( c = 2) for “stick” and “slip” boundary conditions, respectively.…”

Section: Resultsmentioning

confidence: 93%

Computing Accurate True Self-Diffusion Coefficients and Shear Viscosities Using the OrthoBoXY Approach

Busch,

Paschek

2024

J. Phys. Chem. B

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7983−7987], we have shown that for molecular dynamics (MD) simulations using orthorhombic periodic boundary conditions with "magic" box length ratios of L z / L x = L z /L y = 2.7933596497, the self-diffusion coefficients D x and D y in x-and ydirections are independent of the system size. They both represent the true selfdiffusion coefficient D 0 = (D x + D y )/2, while the shear viscosity can be calculated from diffusion coefficients in x-, y-, and z-directions,In this contribution, we test this "OrthoBoXY" approach by its application to a variety of different systems: liquid water, dimethyl ether, methanol, triglyme, water/methanol mixtures, water/triglyme mixtures, and imidazolium-based ionic liquids. The chosen systems range from small-sized molecular liquids to complex mixtures and ionic liquids, while spanning a viscosity range of almost 3 orders of magnitude. We assess the efficiency of the method for computing true self-diffusion and viscosity data and provide simple formulas for estimating the required MD simulation lengths and sizes for delivering reliable data with targeted uncertainty levels. Our analysis of the system size dependence of statistical uncertainties for both the viscosity and the self-diffusion coefficient leads us to the conclusion that it is preferable to extend the simulation length instead of increasing the system size. MD simulations consisting of 768 molecules or ion pairs seem to be perfectly adequate.

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Diffusion, viscosity, and Stokes-Einstein relation in dense supercritical methane

Cited by 17 publications

References 28 publications

Correlations between the Shear Viscosity and Thermal Conductivity Coefficients of Dense Simple Liquids

Correlations between the Shear Viscosity and Thermal Conductivity Coefficients of Dense Simple Liquids

Stokes–Einstein relation without hydrodynamic diameter in the TIP4P/Ice water model

Computing Accurate True Self-Diffusion Coefficients and Shear Viscosities Using the OrthoBoXY Approach

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