On the existence of a hysteresis loop in open and closed end pores

Fan, Chunyan, Do, D. D. and Nicholson, D. (2014) On the existence of a hysteresis loop in open and closed end pores. Molecular Simulation, 41 4: 245-255. doi:10.1080/08927022.2013.869805


Author Fan, Chunyan
Do, D. D.
Nicholson, D.
Title On the existence of a hysteresis loop in open and closed end pores
Journal name Molecular Simulation   Check publisher's open access policy
ISSN 0892-7022
Publication date 2014-01-16
Year available 2014
Sub-type Article (original research)
DOI 10.1080/08927022.2013.869805
Open Access Status
Volume 41
Issue 4
Start page 245
End page 255
Total pages 11
Place of publication Abingdon, Oxfordshire, United Kingdom
Publisher Taylor & Francis
Collection year 2015
Language eng
Abstract We have studied the adsorption of argon at 87 K in slit pores of finite length with a smooth graphitic potential, open at both ends or closed at one end. Simulations were carried out using conventional GCMC (grand canonical Monte Carlo) or kMC (kinetic Monte Carlo) in the canonical ensemble with extremely long Markov chain, of at least 2 × 108 configurations; selected simulations with much longer Markov chains do not show any change in the results. When the pore width is in the micropore range (0.65 nm), type I isotherms are obtained for both pore models and for both simulation methods. However, wider pores (1, 2 and 3 nm in width) all exhibit hysteresis loops in the GCMC simulations, while in the canonical ensemble simulations, the isotherms pass through a sigmoid van der Waals type loop in the transition region. This loop locates the true equilibrium transition. For the pores with one closed end, this transition is close to, or coincides with, the adsorption branch of the GCMC hysteresis loop, but for the open-ended pores, it is more closely associated with the desorption branch. In a separate study of adsorption hysteresis in an infinitely long slit pore, using both simulation techniques, the van der Waals loop follows the adsorption branch of the GCMC isotherm to the transition, then reverts to a long vertical section that falls midway between the two hysteresis branches and finally moves to the desorption transition close to the evaporation pressure. An examination of molecular distributions inside the pores reveals two coexisting phases in the canonical simulations, whereas in the grand canonical simulations, the molecules are uniformly distributed along the length of the pores.
Keyword Adsorption
Monte Carlo simulation
Hysteresis
Slit pore
Closed end pore
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Published online ahead of print 16 January 2014.

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Chemical Engineering Publications
Official 2015 Collection
 
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