Local structure and density fluctuations in confined fluids

Nygård, Kim

doi:10.1016/j.cocis.2016.02.005

Cited by 25 publications

(30 citation statements)

References 39 publications

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“…Due to reduced dimensionality and large surface and interface effects, liquids that are subjected to some geometric constraints on the nanoscale can have different properties to those they display under standard bulk conditions . For instance, the local molecular density profile can show fluctuations, and the extent of layering of molecules across the pore is dependent on the pore radius . X‐ray and neutron scattering experiments on water confined in nanopores have demonstrated that liquid states can persist down to temperatures much lower than in the bulk liquid, and there is also recent evidence that confinement can induce microphase separation of binary liquid mixtures.…”

Section: Figurementioning

confidence: 99%

Confinement Effects on the Benzene Orientational Structure

et al. 2018

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Liquids under confinement exhibit different properties compared with their corresponding bulk phases, for example, miscibility, phase transitions, and diffusion. The underlying cause is the local ordering of molecules, which is usually only studied using pure simulation methods. Herein, we derive experimentally the structure of benzene confined in MCM‐41 using total neutron scattering measurements. The study reveals a layering of molecules across a pore, and four concentric cylindrical shells can be distinguished for a pore with the radius of 18 Å. The nanoscale confinement of the liquid has a major effect on the spatial and orientational correlations observed between the molecules, when compared with the structure of the bulk liquid. These differences are most marked for molecules in parallel configurations, and this suggests differences in chemical reactivity between the confined and bulk liquids.

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Section: Figurementioning

confidence: 99%

Confinement Effects on the Benzene Orientational Structure

et al. 2018

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“…When liquids are confined into a nanometer-scale slit, they often exhibit layered structures [5,6], much enhanced shear viscosity [7][8][9], and oscillatory solvation forces while being continuously compressed [5,10,11]. Those characteristics, deviating from the bulk, are typically due to perturbation (i.e., the presence of confining surfaces) induced molecular ordering, which is inherently a natural consequence of liquid wavenumber dependent compressibility [12,13].…”

Section: Introductionmentioning

confidence: 99%

“…In the framework of a density-functional theory based description [12][13][14][15], one may discern that one-particle density of a confined liquid holds a similar functional form as that of the two-particle density of a bulk liquid. Such a similarity has been confirmed by recent simulation works [16,17].…”

Section: Introductionmentioning

confidence: 99%

History-dependent Stress Relaxation of Liquids Under High-confinement: A Molecular Dynamics Study

Gao¹

2021

Preprint

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When liquids are confined into nanometer-scale slit, the induced layering-like film structure allows the liquid to sustain non-isotropic stresses and thus being load-bearing. Such anisotropic characteristics of liquid under confinement arise naturally from the liquids’ wave number dependent compressibility that does not need solidification to take place as a prerequisite. In other words, liquids under confinement can still remain fluidity with molecules being (sub-)diffusive. However, the extensively prolonged structural relaxation time can cause hysteresis of stress relaxation of confined molecules in response to the motions of confining walls and thereby yield the quasi-static stress tensor history-dependent. In this work, by means of molecule dynamics, the discrepancy of stress tensor of a highly confined key base-oil component, i.e. 1-decene trimer, is captured after its relaxation from being compressed and decompressed. The results indicate that among the effects (e.g. confinement, molecular structure, and film density) that can potentially affect confined stress tensor, the ordering status of the confined molecules plays a predominant role.

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“…[1] Due to reduced dimensionality and large surface and interface effects,l iquids that are subjected to some geometric constraints on the nanoscale can have different properties to those they display under standard bulk conditions. [3] X-ray and neutron scattering experiments on water confined in nanopores have demonstrated that liquid states can persist down to temperatures much lower than in the bulk liquid, [4] and there is also recent evidence that confinement can induce microphase separation of binary liquid mixtures.S uch phe-nomena have been reported for aqueous solutions of glycerol, [5] and for tert-butanol and toluene binary mixtures [6] confined in MCM-41, although these solutes are fully miscible under bulk solution conditions.U nderstanding the structure of confined liquids is,therefore,animportant factor that can help explain why liquid properties change when molecular interactions are subject to nanoscale steric constraints. [3] X-ray and neutron scattering experiments on water confined in nanopores have demonstrated that liquid states can persist down to temperatures much lower than in the bulk liquid, [4] and there is also recent evidence that confinement can induce microphase separation of binary liquid mixtures.S uch phe-nomena have been reported for aqueous solutions of glycerol, [5] and for tert-butanol and toluene binary mixtures [6] confined in MCM-41, although these solutes are fully miscible under bulk solution conditions.U nderstanding the structure of confined liquids is,therefore,animportant factor that can help explain why liquid properties change when molecular interactions are subject to nanoscale steric constraints.…”

mentioning

confidence: 99%

“…[2] Fori nstance,t he local molecular density profile can show fluctuations,a nd the extent of layering of molecules across the pore is dependent on the pore radius. [3] X-ray and neutron scattering experiments on water confined in nanopores have demonstrated that liquid states can persist down to temperatures much lower than in the bulk liquid, [4] and there is also recent evidence that confinement can induce microphase separation of binary liquid mixtures.S uch phe-nomena have been reported for aqueous solutions of glycerol, [5] and for tert-butanol and toluene binary mixtures [6] confined in MCM-41, although these solutes are fully miscible under bulk solution conditions.U nderstanding the structure of confined liquids is,therefore,animportant factor that can help explain why liquid properties change when molecular interactions are subject to nanoscale steric constraints.…”

mentioning

confidence: 99%