Journal ArticleDOI
Molecular dynamics of flow in micropores
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TLDR
In this paper, a local average density model (LADM) is proposed for strongly inhomogeneous fluids. But the model is not suitable for the case of a single micropore.Abstract:
The method of nonequilibrium molecular dynamics is used to study the viscosity and flow properties of strongly inhomogeneous liquids, a particular case of which is a liquid confined in a micropore only a few molecular diameters wide. Fluid inhomogeneity is introduced by imposing an external potential that in one case simulates flat solid walls and in the other case causes density peaks in the middle of a thin liquid film. For comparison a homogeneous fluid is also simulated. In both types of inhomogeneous fluid, the shear stress and effective viscosity are smaller than in the homogeneous fluid. The density profiles and the diffusivities in the micropore were found to be independent of flow, even at the extremely high rates, 1010–1011 s−1 of the simulation. The Green–Kubo relation is found to be valid for the diffusivity under the flow studied. We propose a local average density model (LADM) of viscosity and diffusivity, in which the local transport coefficients are those of homogeneous fluid at a mean density obtained by averaging the local density over a molecular volume. LADM predicts qualitatively correct velocity profiles, effective viscosities, and shear stresses using only equilibrium density profiles and molecular diameters. An analogous local equilibrium version of Enskog’s theory of diffusivity agrees well with the simulated pore diffusivities. Recently Vanderlick and Davis generalized Enskog’s theory of diffusivity to strongly inhomogeneous fluids. Their theoretical pore diffusion coefficient is also in good agreement with simulation results.read more
Citations
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Journal ArticleDOI
Motions and relaxations of confined liquids
TL;DR: When a liquid is confined in a narrow gap, the effective shear viscosity is enhanced compared to the bulk, relaxation times are prolonged, and nonlinear responses set in at lower shear rates.
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Dynamic Properties of Molecularly Thin Liquid Films
TL;DR: Results show that two molecularly smooth surfaces, when close together in simple liquids, slide (shear) past each other while separated by a discrete number of molecular layers, and that the frictional force is "quantized" with the number of layers.
Journal ArticleDOI
Confinement-induced phase transitions in simple liquids.
Jacob Klein,Eugenia Kumacheva +1 more
TL;DR: The liquid-to-solid transition of a simple model liquid confined between two surfaces was studied as a function of surface separation and the rigidity of the confined films increased reversibly by at least seven orders of magnitude.
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Molecular simulation of water in carbon nanotubes.
TL;DR: This work describes the physical properties of carbon nanotubes as well as the theoretical models used to derive these properties, and shows how these properties can be modified to improve the quality of the research.
Journal ArticleDOI
Simple liquids confined to molecularly thin layers. I. Confinement-induced liquid-to-solid phase transitions
Jacob Klein,Eugenia Kumacheva +1 more
TL;DR: In this paper, a surface force balance with extremely high resolution in measuring shear forces has been used to study the properties of films of the simple organic solvents cyclohexane, octamethylcyclotetrasiloxane, and toluene, confined in a gap between smooth solid surfaces.
References
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TL;DR: The dynamique des : fluides Reference Record created on 2005-11-18 is updated on 2016-08-08 and shows improvements in the quality of the data over the past decade.
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Computer "Experiments" on Classical Fluids. I. Thermodynamical Properties of Lennard-Jones Molecules
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Statistical-Mechanical Theory of Irreversible Processes : I. General Theory and Simple Applications to Magnetic and Conduction Problems
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Molecular dynamics simulations at constant pressure and/or temperature
TL;DR: In this paper, it is shown that time averages of properties of the simulated fluid are equal to averages over the isoenthalpic-isobaric, canonical, and isothermal-isboric ensembles.