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Soft-wall induced structure and dynamics of partially confined supercritical fluids
Kanka Ghosh,
Published in American Institute of Physics Inc.
2019
PMID: 30901989
Volume: 150
   
Issue: 11
Abstract
The interplay between the structure and dynamics of partially confined Lennard Jones (LJ) fluids, deep into the supercritical phase, is studied over a wide range of densities in the context of the Frenkel line (FL), which separates rigid liquidlike and non-rigid gaslike regimes in the phase diagram of the supercritical fluids. Extensive molecular dynamics simulations carried out at the two ends of the FL (P = 5000 bars, T = 300 K, and T = 1500 K) reveal intriguing features in supercritical fluids as a function of stiffness of the partially confining atomistic walls. The liquidlike regime of a LJ fluid (P = 5000 bars, T = 300 K), mimicking argon, partially confined between walls separated by 10 Å along the z-axis, and otherwise unconstrained, reveals amorphous and liquidlike structural signatures in the radial distribution function parallel to the walls and enhanced self-diffusion as the wall stiffness is decreased. In sharp contrast, in the gas-like regime (P = 5000 bars, T = 1500 K), soft walls lead to increasing structural order hindering self-diffusion. Furthermore, the correlations between the structure and self-diffusion are found to be well captured by excess entropy. The rich behaviour shown by supercritical fluids under partial confinement, even with simple interatomic potentials, is found to be fairly independent of hydrophilicity and hydrophobicity. The study identifies persisting sub-diffusive features over intermediate time scales, emerging from the strong interplay between density and confinement, to dictate the evolution and stabilization of structures. It is anticipated that these results may help gain a better understanding of the behaviour of partially confined complex fluids found in nature. © 2019 Author(s).
About the journal
JournalData powered by TypesetJournal of Chemical Physics
PublisherData powered by TypesetAmerican Institute of Physics Inc.
ISSN00219606
Open AccessYes
Concepts (15)
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    Diffusion in liquids
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    Distribution functions
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    Effluent treatment
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    Molecular dynamics
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    Stiffness
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    Supercritical fluids
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    INTERATOMIC POTENTIAL
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    LENNARD JONES FLUID
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    Molecular dynamics simulations
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    Radial distribution functions
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    STRUCTURAL ORDERING
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    STRUCTURAL SIGNATURES
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    Structure and dynamics
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    SUPERCRITICAL PHASE
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    Rigid structures