Liquid-liquid phase transition in simple Lennard-Jones nano-confined fluids

Sheibani, Narjes; Kamalvand, Mohammad

doi:10.1016/j.fluid.2020.112495

Cited by 6 publications

(4 citation statements)

References 24 publications

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“…Various analytical and numerical methods have been examined to predict and model the above theory for pure normal fluids, e.g., developed microscopic van der Waals (vdW) equation of state (EOS) in a similar previous study 6 , molecular dynamics simulation (MD) 7 , density functional theory 8 , lattice Boltzmann method (LBM) 9 , scaled particle theory (SPT or RFL) 10 , and different classes of Monte Carlo simulations 11 – 19 .…”

Section: Introductionmentioning

confidence: 99%

“…Because of the occurrence of critical shift in confined media, applying the bulk properties of matters undoubtedly leads to poor results when calculating vapor-liquid equilibrium (VLE) properties of their confined state. Various analytical and numerical methods have been examined to predict and model the above theory for pure normal fluids, e.g., developed microscopic van der Waals (vdW) equation of state (EOS) in a similar previous study 6 , molecular dynamics simulation (MD) 7 , density functional theory 8 , lattice Boltzmann method (LBM) 9 , scaled particle theory (SPT or RFL) 10 , and different classes of Monte Carlo simulations [11][12][13][14][15][16][17][18][19] .…”

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confidence: 99%

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Critical temperature shift modeling of confined fluids using pore-size-dependent energy parameter of potential function

Humand

Movaghar

2023

Sci Rep

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The behavior and critical properties of fluids confined in nanoscale porous media differ from those of bulk fluids. This is well known as critical shift phenomenon or pore proximity effect among researchers. Fundamentals of critical shift modeling commenced with developing equations of state (EOS) based on the Lennard–Jones (L–J) potential function. Although these methods have provided somewhat passable predictions of pore critical properties, none represented a breakthrough in basic modeling. In this study, a cubic EOS is derived in the presence of adsorption for Kihara fluids, whose attractive term is a function of temperature. Accordingly, the critical temperature shift is modeled, and a new adjustment method is established in which, despite previous works, the bulk critical conditions of fluids are reliably met with a thermodynamic basis and not based on simplistic manipulations. Then, based on the fact that the macroscopic and microscopic theories of corresponding states are related, an innovative idea is developed in which the energy parameter of the potential function varies with regard to changes in pore size, and is not taken as a constant. Based on 94 available data points of critical shift reports, it is observed that despite L–J, the Kihara potential has sufficient flexibility to properly fit the variable energy parameters, and provide valid predictions of phase behavior and critical properties of fluids. Finally, the application of the proposed model is examined by predicting the vapor–liquid equilibrium properties of a ternary system that reduced the error of the L–J model by more than 6%.

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%

Critical temperature shift modeling of confined fluids using pore-size-dependent energy parameter of potential function

Humand

Movaghar

2023

Sci Rep

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“…Moreover, nanoscale interaction had a remarkable effect on the gas-liquid equilibrium. The phase behavior of fluids confined at the nanoscale shows distinct characteristic features from that in bulk phase [1][2][3][4][5][6][7][8][9][10][11][12][13] which is very difficult to quantify in experiments. * Author to whom any correspondence should be addressed.…”

Section: Introductionmentioning

confidence: 99%

Role of site–site interaction on the phase equilibria of multiple-site associating fluids in a functionalized slit pore

Mandal,

Singh,

Khan

2023

J. Phys.: Condens. Matter

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Vapor-liquid phase equilibria for multiple sites associating fluids with different associating strengths are investigated in a slit pore using Grand-Canonical Transition Matrix Monte Carlo (GC-TMMC) method. The increase of critical temperature from two-site to four-site associating fluids at constant site strength is quite significant as compared to that of the one-site to two-site associating fluids, which is more pronounced at higher associating strength (ε*=6). Monomer fraction and cluster size distribution are used to investigate the association of fluid particles in coexistence phases. The monomer fraction for both phases decreases with increased associating sites on the fluid particles due to more site-site interaction with neighbouring fluid particles and forming a larger cluster. Therefore, the number of associating sites and their distribution play a vital role in the association of fluid particles. Moreover, the saturation chemical potential changes with the arrangement of the sites. For two-site associating fluids, we observe early vapor-liquid transition when the sites are oppositely placed, and when the sites are placed at 90 degrees, the vapor-liquid transition is observed at the higher chemical potential. Moreover, four-site associating fluids with a square arrangement show early vapor-liquid phase transition, mainly because these arrangements of sites effectively interact with surface sites and the molecules in the next layer.

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“…Molecular dynamics (MD) simulation is a powerful tool which can be used to obtain microscopic insights into the properties of confined liquids behind the experimental results and to guide future research applications. Several studies have been conducted using both equilibrium and non-equilibrium MD simulations on confined liquids such as Lennard-Jones (LJ) particles [22][23][24] , water 11,14,25,26 , and hydrocarbons [27][28][29] . A recent simulation conducted by Ta et al 27 of a hexadecane film confined between iron oxide surfaces demonstrated that an increase in the shear rate can result in a decrease in the degree of ordering of the hexadecane film and an increase in the velocity slip at the solid-liquid interfaces.…”

Section: Introductionmentioning

confidence: 99%

Correlation between ordering and shear thinning in confined liquids

Kobayashi¹,

Arai²,

Yasuoka³

2022

Preprint

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Despite the extensive research that has been conducted for decades on the behavior of confined liquids, detailed knowledge of this phenomenon, particularly in the mixed/boundary lubrication regime, remains limited. This can be attributed to several factors including the difficulty of direct experimental observations of the behavior of lubricant molecules under non-equilibrium conditions, the high computational cost of molecular simulations to reach steady state, and the low signal-to-noise ratio at extremely low shear rates corresponding to actual operating conditions. To this end, we studied the correlation between the structure formation and shear viscosity of octamethylcyclotetrasiloxane confined between two mica surfaces in a mixed/boundary lubrication regime. Three different surface separations corresponding to two-, three-, and five-layered structures were considered to analyze the effect of confinement. The orientational distributions with one specific peak for n = 2 and two distributions, including a parallel orientation with the surface normal for n > 2, were observed at rest. The confined liquids exhibited a distinct shear-thinning behavior independent of surface separations for a relatively low sliding velocity, V x 10 −1 m/s. However, the shear viscosities at V x 10 −1 m/s depended on the number of layered structures. Newtonian behavior was observed with a further increase in the sliding velocity. Furthermore, we found a strong correlation between the degree of molecular orientation and the shear viscosity of the confined liquids. The magnitude of the shear viscosity of the confined liquids can primarily be determined by the degree of molecular orientation, and shear-thinning originates from the vanishing of specific orientational distributions with increasing sliding velocity.

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Liquid-liquid phase transition in simple Lennard-Jones nano-confined fluids

Cited by 6 publications

References 24 publications

Critical temperature shift modeling of confined fluids using pore-size-dependent energy parameter of potential function

Critical temperature shift modeling of confined fluids using pore-size-dependent energy parameter of potential function

Role of site–site interaction on the phase equilibria of multiple-site associating fluids in a functionalized slit pore

Correlation between ordering and shear thinning in confined liquids

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