A thermodynamic study of the mid-density scheme to determine the equilibrium phase transition in cylindrical pores

Liu, Zhongjun; Dang, Duong; Nicholson, D.

doi:10.1080/08927022.2011.613383

Cited by 10 publications

(8 citation statements)

References 30 publications

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“…A number of points, which may not have been widely recognized, are listed below: There is hysteresis in both open- and closed-end pores, but the loop for the open-end pore is significantly larger. The change in density on adsorption is vertical in the open-end pore, but, although sharp, it is not vertical in the closed-end pore. The onset of condensation for the open-end pore (point C) occurs at a higher pressure than the for corresponding closed-end pore, and the pore density just before the jump is also higher. The adsorbed density just before condensation is always higher than that just after evaporation for both open-end and closed-end pores. This is referred to as delayed condensation in the literature because the condensation occurs at a pressure higher than the equilibrium pressure. Both desorption boundaries for the open-end and closed-end pores have a knee (from F to G) just before evaporation. The equilibrium transitions (dashed line) are second order for both open- and closed-end pores, in contrast to the first-order transitions in pores of infinite length. ,, The equilibrium branch is closer to the desorption branch for the open-end pore but to the adsorption branch for the closed-end pore. …”

Section: Resultsmentioning

confidence: 93%

Anatomy of Adsorption in Open-End and Closed-End Slit Mesopores: Adsorption, Desorption, and Equilibrium Branches of Hysteresis Loop

Zeng

Phadungbut

et al. 2014

J. Phys. Chem. C

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We present a detailed analysis, using simulated data, of the adsorption and desorption in two finite length slit mesopores, one with both ends open to the surroundings and the other with one end closed, to investigate the microscopic behavior of an adsorbate in a confined space. The mesoscopic analysis of the interface separating the gas-like phase and the condensed phase reveals the mechanisms that lead to hysteresis in these two types of pore. The effects of pore width, temperature, and surface strength on these mechanisms are also studied to probe the detailed behavior of the system just before condensation and just after evaporation. In particular, for closed-end pores, we observe the development of a meniscus and the subsequent movement of the developed meniscus in adsorption and desorption. From these observations we are able to explain why adsorption and desorption branches have two distinct sections, slow and fast variations with pressure (corresponding to the two stages (1) developing meniscus and (2) developed meniscus), which have not been recognized in earlier literature.

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Section: Resultsmentioning

confidence: 93%

Anatomy of Adsorption in Open-End and Closed-End Slit Mesopores: Adsorption, Desorption, and Equilibrium Branches of Hysteresis Loop

Zeng

Phadungbut

et al. 2014

J. Phys. Chem. C

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“…On a rectangular surface, two phases coexist in strip form and there is a vertical segment in the middle of the unstable branches of the loop. The equilibrium phase transition determined by the MDS [32,33] was found to coincide with the vertical segment of the vdW-like loops in the meso-canonical isotherms, adding further support to the validity of the MDS.…”

Section: Discussionmentioning

confidence: 64%

“…The mid-density scheme (MDS) developed by Liu et al [32,33] to determine the equilibrium transition in the hysteresis loop of capillary condensation in mesoporous solids was applied to locate the 2D-transition of the adsorbed argon at temperatures less than the 2D-critical temperature. At a given chemical potential m* in the hysteresis loop, the two states on the hysteresis boundary are N A and N B .…”

Section: Mid-density Schemementioning

confidence: 99%

On the phase transition in a monolayer adsorbed on graphite at temperatures below the 2D-critical temperature

Phadungbut

Nguyen

et al. 2014

Molecular Simulation

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Monte Carlo simulations in the grand ensemble and meso-canonical ensemble in which the adsorbent is connected to a finite reservoir have been used to study adsorption isotherms for monolayer argon adsorption on graphite at temperatures below the 2D-critical temperature in order to elucidate the microscopic details of the 2D-transitions: vapour-solid, vapour-liquid and liquid-solid. An S-shaped van der Waals (vdW) loop was found when a small square surface was used; however, for large square surfaces and rectangular surfaces the isotherms exhibit a vdW-type loop with a vertical segment which indicates the coexistence of two phases separated by a boundary that changes its shape with the loading. This coexistence occurs at the same chemical potential as determined by the mid-density scheme, developed by Do and co-workers (Z. Liu, L. Herrera, V.T. Nguyen, D.D. Do, and D. Nicholson, A Monte Carlo scheme based on mid-density in a hysteresis loop to determine equilibrium phase transition. Mol Simul. 37(11):932-939, 2011; Z. Liu, D.D. Do, and D. Nicholson, A thermodynamic study of the mid-density scheme to determine the equilibrium phase transition in cylindrical pores. Mol Simul. 38(3):189-199, 2011).

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“…Compared with conventional but computationally expensive methods, the middensity scheme is a simplified but useful approach to identify the equilibrium phase transition in a hysteresis loop [33]. It has been successfully applied to study argon adsorption in graphite slit pores and in silica cylindrical pores [33,44]. The researchers who proposed this method also demonstrated [45] that its validity for the determination of the equilibrium state is supported by the commonly used canonical ensemble kinetic Monte Carlo (CE-kMC) [46,47] and gauge cell methods [36,37,48].…”

Section: Simulation Models and Methodsmentioning

confidence: 99%

Computational Simulations of Nanoconfined Argon Film through Adsorption–Desorption in a Uniform Slit Pore

Rao

Xiang

et al. 2021

Coatings

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We performed hybrid grand canonical Monte Carlo/molecular dynamics (GCMC/MD) simulations to investigate the adsorption-desorption isotherms of argon molecules confined between commensurate and incommensurate contacts in nanoscale thickness. The recently proposed mid-density scheme was applied to the obtained hysteresis loops to produce a realistic equilibrium phase of nanoconfined fluids. The appropriate chemical potentials can be determined if the equilibrium structures predicted by GCMC/MD simulations are consistent with those observed in previously developed liquid-vapor molecular dynamics (LVMD) simulations. With the chemical potential as input, the equilibrium structures obtained by GCMC/MD simulations can be used as reasonable initial configurations for future metadynamics free energy calculations.

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A thermodynamic study of the mid-density scheme to determine the equilibrium phase transition in cylindrical pores

Cited by 10 publications

References 30 publications

Anatomy of Adsorption in Open-End and Closed-End Slit Mesopores: Adsorption, Desorption, and Equilibrium Branches of Hysteresis Loop

Anatomy of Adsorption in Open-End and Closed-End Slit Mesopores: Adsorption, Desorption, and Equilibrium Branches of Hysteresis Loop

On the phase transition in a monolayer adsorbed on graphite at temperatures below the 2D-critical temperature

Computational Simulations of Nanoconfined Argon Film through Adsorption–Desorption in a Uniform Slit Pore

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