1
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Nguyen MD, Simon J, Scott JW, Zimmerman AM, Tsai YCC, Halperin WP. Orbital-flop transition of superfluid 3He in anisotropic silica aerogel. Nat Commun 2024; 15:201. [PMID: 38172106 PMCID: PMC10764773 DOI: 10.1038/s41467-023-44557-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Accepted: 12/12/2023] [Indexed: 01/05/2024] Open
Abstract
Superfluid 3He is a paradigm for odd-parity Cooper pairing, ranging from neutron stars to uranium-based superconducting compounds. Recently it has been shown that 3He, imbibed in anisotropic silica aerogel with either positive or negative strain, preferentially selects either the chiral A-phase or the time-reversal-symmetric B-phase. This control over basic order parameter symmetry provides a useful model for understanding imperfect unconventional superconductors. For both phases, the orbital quantization axis is fixed by the direction of strain. Unexpectedly, at a specific temperature Tx, the orbital axis flops by 90∘, but in reverse order for A and B-phases. Aided by diffusion limited cluster aggregation simulations of anisotropic aerogel and small angle X-ray measurements, we are able to classify these aerogels as either "planar" and "nematic" concluding that the orbital-flop is caused by competition between short and long range structures in these aerogels.
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Affiliation(s)
- M D Nguyen
- Department of Physics and Astronomy, Northwestern University, Evanston, IL, 60208, USA.
| | - Joshua Simon
- Department of Physics and Astronomy, Northwestern University, Evanston, IL, 60208, USA
| | - J W Scott
- Department of Physics and Astronomy, Northwestern University, Evanston, IL, 60208, USA
| | - A M Zimmerman
- Department of Physics and Astronomy, Northwestern University, Evanston, IL, 60208, USA
| | - Y C Cincia Tsai
- Department of Physics and Astronomy, Northwestern University, Evanston, IL, 60208, USA
| | - W P Halperin
- Department of Physics and Astronomy, Northwestern University, Evanston, IL, 60208, USA.
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2
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Martin E, Prostredny M, Fletcher A, Mulheran P. Advancing Computational Analysis of Porous Materials-Modeling Three-Dimensional Gas Adsorption in Organic Gels. J Phys Chem B 2021; 125:1960-1969. [PMID: 33591747 PMCID: PMC8023708 DOI: 10.1021/acs.jpcb.0c11000] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 02/02/2021] [Indexed: 11/29/2022]
Abstract
Assessing the efficacy of specific porous materials for use in various applications has been a central focus for many experimental studies over the years, with a view to altering the material properties according to the desired characteristics. The application potential for one such class of nanoporous materials-organic resorcinol-formaldehyde (RF) gels-is of particular interest, due to their attractive and adjustable properties. In this work, we simulate adsorption analysis using lattice-based mean field theory, both in individual pores and within three-dimensional porous materials generated from a kinetic Monte Carlo cluster aggregation model. We investigate the impacts of varying pore size and geometry on the adsorptive behavior, with results agreeing with those previously postulated in the literature. The adsorption analysis is carried out for porous materials simulated with varying catalyst concentrations and solids contents, allowing their structural properties to be assessed from resulting isotherms and the adsorption and desorption processes visualized using density color maps. Isotherm analysis indicated that both low catalyst concentrations and low solids contents resulted in structures with open transport pores that were larger in width, while high catalyst concentrations and solids contents resulted in structures with bottleneck pores that were narrower. We present results from both the simulated isotherms and pore size analysis distributions, in addition to results from RF gels synthesized in the lab and analyzed experimentally, with significant similarities observed between the two. Not only do the results of this comparison validate the kinetic Monte Carlo model's ability to successfully capture the formation of RF gels under varying synthesis parameters, but they also show significant promise for the tailoring of material properties in an efficient and computationally inexpensive manner-something which would be pivotal in realizing their full application potential, and could be applied to other porous materials whose formation mechanism operates under similar principles.
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Affiliation(s)
- Elisha Martin
- Department of Chemical &
Process Engineering, University of Strathclyde, Glasgow G1 1XL, United Kingdom
| | - Martin Prostredny
- Department of Chemical &
Process Engineering, University of Strathclyde, Glasgow G1 1XL, United Kingdom
| | - Ashleigh Fletcher
- Department of Chemical &
Process Engineering, University of Strathclyde, Glasgow G1 1XL, United Kingdom
| | - Paul Mulheran
- Department of Chemical &
Process Engineering, University of Strathclyde, Glasgow G1 1XL, United Kingdom
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3
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Rimas Z, Taraskin SN. A single-walker approach for studying quasi-nonergodic systems. Sci Rep 2017; 7:2242. [PMID: 28533539 PMCID: PMC5440385 DOI: 10.1038/s41598-017-01704-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Accepted: 03/30/2017] [Indexed: 11/09/2022] Open
Abstract
The jump-walking Monte-Carlo algorithm is revisited and updated to study the equilibrium properties of systems exhibiting quasi-nonergodicity. It is designed for a single processing thread as opposed to currently predominant algorithms for large parallel processing systems. The updated algorithm is tested on the Ising model and applied to the lattice-gas model for sorption in aerogel at low temperatures, when dynamics of the system is critically slowed down. It is demonstrated that the updated jump-walking simulations are able to produce equilibrium isotherms which are typically hidden by the hysteresis effect characteristic of the standard single-flip simulations.
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Affiliation(s)
- Zilvinas Rimas
- Sidney Sussex College and Department of Chemistry, University of Cambridge, Cambridge, UK.
| | - Sergei N Taraskin
- St. Catharine's College and Department of Chemistry, University of Cambridge, Cambridge, UK
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4
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Hughes AP, Thiele U, Archer AJ. Liquid drops on a surface: Using density functional theory to calculate the binding potential and drop profiles and comparing with results from mesoscopic modelling. J Chem Phys 2015; 142:074702. [DOI: 10.1063/1.4907732] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Affiliation(s)
- Adam P. Hughes
- Department of Mathematical Sciences, Loughborough University, Loughborough LE11 3TU, United Kingdom
| | - Uwe Thiele
- Westfälische Wilhelms-Universität Münster, Institut für Theorestische Physik, Wilhelm-Klemm-Str. 9, 48149 Münster, Germany
- Center of Nonlinear Science (CeNoS), Westfälische Wilhelms Universität Münster, Corrensstr. 2, 48149 Münster, Germany
- Center for Multiscale Theory and Computation (CMTC), University of Münster, Corrensstr. 40, 48149 Münster, Germany
| | - Andrew J. Archer
- Department of Mathematical Sciences, Loughborough University, Loughborough LE11 3TU, United Kingdom
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5
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Aubry GJ, Bonnet F, Melich M, Guyon L, Spathis P, Despetis F, Wolf PE. Condensation of helium in aerogel and athermal dynamics of the random-field Ising model. PHYSICAL REVIEW LETTERS 2014; 113:085301. [PMID: 25192103 DOI: 10.1103/physrevlett.113.085301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Indexed: 06/03/2023]
Abstract
High resolution measurements reveal that condensation isotherms of (4)He in high porosity silica aerogel become discontinuous below a critical temperature. We show that this behavior does not correspond to an equilibrium phase transition modified by the disorder induced by the aerogel structure, but to the disorder-driven critical point predicted for the athermal out-of-equilibrium dynamics of the random-field Ising model. Our results evidence the key role of nonequilibrium effects in the phase transitions of disordered systems.
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Affiliation(s)
- Geoffroy J Aubry
- Université Grenoble Alpes, Institut Néel, F-38042 Grenoble, France and CNRS, Institut Néel, F-38042 Grenoble, France
| | - Fabien Bonnet
- Université Grenoble Alpes, Institut Néel, F-38042 Grenoble, France and CNRS, Institut Néel, F-38042 Grenoble, France
| | - Mathieu Melich
- Université Grenoble Alpes, Institut Néel, F-38042 Grenoble, France and CNRS, Institut Néel, F-38042 Grenoble, France
| | - Laurent Guyon
- Université Grenoble Alpes, Institut Néel, F-38042 Grenoble, France and CNRS, Institut Néel, F-38042 Grenoble, France
| | - Panayotis Spathis
- Université Grenoble Alpes, Institut Néel, F-38042 Grenoble, France and CNRS, Institut Néel, F-38042 Grenoble, France
| | - Florence Despetis
- Université Montpellier 2, Laboratoire Charles Coulomb UMR 5221, F-34095 Montpellier, France and CNRS, Laboratoire Charles Coulomb UMR 5221, F-34095 Montpellier, France
| | - Pierre-Etienne Wolf
- Université Grenoble Alpes, Institut Néel, F-38042 Grenoble, France and CNRS, Institut Néel, F-38042 Grenoble, France
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6
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Puibasset J, Kierlik E, Tarjus G. Influence of system size on the properties of a fluid adsorbed in a nanopore: Physical manifestations and methodological consequences. J Chem Phys 2014; 141:044716. [PMID: 25084946 DOI: 10.1063/1.4891359] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Hysteresis and discontinuities in the isotherms of a fluid adsorbed in a nanopore in general hamper the determination of equilibrium thermodynamic properties, even in computer simulations. A way around this has been to consider both a reservoir of small size and a pore of small extent in order to restrict the fluctuations of density and approach a classical van der Waals loop. We assess this suggestion by thoroughly studying through Monte Carlo simulations and density functional theory the influence of system size on the equilibrium configurations of the adsorbed fluid and on the resulting isotherms. We stress the importance of pore-symmetry-breaking states that even for modest pore sizes lead to discontinuous isotherms and we discuss the physical relevance of these states and the methodological consequences for computing thermodynamic quantities.
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Affiliation(s)
- Joël Puibasset
- CRMD, CNRS FRE 3520, Université d'Orléans, 1b rue de la Férollerie, 45071 Orléans Cedex 02, France
| | - Edouard Kierlik
- LPTMC, CNRS UMR 7600, Université Pierre et Marie Curie, boîte 121, 4 place Jussieu, 75252 Paris Cedex 05, France
| | - Gilles Tarjus
- LPTMC, CNRS UMR 7600, Université Pierre et Marie Curie, boîte 121, 4 place Jussieu, 75252 Paris Cedex 05, France
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7
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Puibasset J. Fluid adsorption in linear pores: a molecular simulation study of the influence of heterogeneities on the hysteresis loop and the distribution of metastable states. MOLECULAR SIMULATION 2014. [DOI: 10.1080/08927022.2013.829221] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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8
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Handford TP, Pérez-Reche FJ, Taraskin SN. Capillary condensation in one-dimensional irregular confinement. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 88:012139. [PMID: 23944446 DOI: 10.1103/physreve.88.012139] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 05/30/2013] [Indexed: 06/02/2023]
Abstract
A lattice-gas model with heterogeneity is developed for the description of fluid condensation in finite sized one-dimensional pores of arbitrary shape. Mapping to the random-field Ising model allows an exact solution of the model to be obtained at zero-temperature, reproducing the experimentally observed dependence of the amount of fluid adsorbed in the pore on external pressure. It is demonstrated that the disorder controls the sorption for long pores and can result in H2-type hysteresis. Finite-temperature Metropolis dynamics simulations support analytical findings in the limit of low temperatures. The proposed framework is viewed as a fundamental building block of the theory of capillary condensation necessary for reliable structural analysis of complex porous media from adsorption-desorption data.
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Affiliation(s)
- Thomas P Handford
- Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, United Kingdom.
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9
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Coasne B, Galarneau A, Pellenq RJM, Di Renzo F. Adsorption, intrusion and freezing in porous silica: the view from the nanoscale. Chem Soc Rev 2013; 42:4141-71. [PMID: 23348418 DOI: 10.1039/c2cs35384a] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Benoit Coasne
- Institut Charles Gerhardt Montpellier, CNRS (UMR 5253), University Montpellier 2, ENSCM, 8 rue de l'Ecole Normale, 34296 Montpellier, France.
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10
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Tarjus G, Rosinberg ML, Kierlik E, Tissier M. Hierarchical reference theory of critical fluids in disordered porous media. Mol Phys 2011. [DOI: 10.1080/00268976.2011.620024] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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11
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Puibasset J. Stability intervals of metastable states in hysteretic systems. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 84:061126. [PMID: 22304059 DOI: 10.1103/physreve.84.061126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Revised: 09/19/2011] [Indexed: 05/31/2023]
Abstract
Hysteresis in disordered systems originates in a plethora of metastable states. Previous works focused on their distribution inside the hysteresis. In contrast, an analysis of their range of metastability is proposed. This model, designed to catch the main features of fluid adsorption in porous materials, shows strong evidence that, in the thermodynamic limit, despite that metastable states of finite range can be found, they are exponentially dominated by those infinitely localized states.
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Affiliation(s)
- Joël Puibasset
- CRMD, CNRS-Université d'Orléans, 1b rue de la Férollerie, F-45071 Orléans Cedex 02, France.
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12
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Horikawa T, Do DD, Nicholson D. Capillary condensation of adsorbates in porous materials. Adv Colloid Interface Sci 2011; 169:40-58. [PMID: 21937014 DOI: 10.1016/j.cis.2011.08.003] [Citation(s) in RCA: 161] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 08/26/2011] [Accepted: 08/27/2011] [Indexed: 11/30/2022]
Abstract
Hysteresis in capillary condensation is important for the fundamental study and application of porous materials, and yet experiments on porous materials are sometimes difficult to interpret because of the many interactions and complex solid structures involved in the condensation and evaporation processes. Here we make an overview of the significant progress in understanding capillary condensation and hysteresis phenomena in mesopores that have followed from experiment and simulation applied to highly ordered mesoporous materials such as MCM-41 and SBA-15 over the last few decades.
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Affiliation(s)
- Toshihide Horikawa
- School of Chemical Engineering, University of Queensland, St. Lucia, Qld 4072, Australia
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13
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Brinkman BAW, Dahmen KA. Tuning coupling: discrete changes in runaway avalanche sizes in disordered media. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 84:041129. [PMID: 22181109 DOI: 10.1103/physreve.84.041129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2010] [Indexed: 05/31/2023]
Abstract
Hysteretic systems may exhibit a runaway avalanche in which a large fraction of the constituents of the system collectively change state. It would be very valuable to understand the role that interaction strength between constituents plays in the size of such catastrophic runaway avalanches. We use a simple model, the random field Ising model, to study how the size of the runaway avalanche changes as the coupling between spins, J, is tuned. In particular, we calculate P(S), the distribution of size changes S in the runaway avalanche size as J comes close to a critical value J(c), and find that the distribution scales as P(S)∼S(-τ)D(S(σ)(J/J(c)-1)), with τ and σ critical exponents and D(x) a universal scaling function. In mean field theory we find τ=3/2, σ=1/2, and D(x)=exp[-(3x)(1/σ)/2]. On the basis of these results and previous studies, we also predict that for three dimensions τ=1.6 and σ=0.24.
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Affiliation(s)
- Braden A W Brinkman
- Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street Urbana, Illinois 61801-3080, USA
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14
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Leoni F, Kierlik E, Rosinberg ML, Tarjus G. Spontaneous imbibition in disordered porous solids: a theoretical study of helium in silica aerogels. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:8160-8170. [PMID: 21657217 DOI: 10.1021/la201146h] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We present a theoretical study of spontaneous imbibition of liquid (4)He in silica aerogels focusing on the effect of porosity on the fluid dynamical behavior. We adopt a coarse-grained three-dimensional lattice-gas description like in previous studies of gas adsorption and capillary condensation and use a dynamical mean-field theory, assuming that capillary disorder predominates over permeability disorder as in recent phase-field models of spontaneous imbibition. Our results reveal a remarkable connection between imbibition and adsorption as also suggested by recent experiments. The imbibition front is always preceded by a precursor film, and the classical Lucas-Washburn √t scaling law is generally recovered, although some deviations may exist at large porosity. Moreover, the interface roughening is modified by wetting and confinement effects. Our results suggest that the interpretation of the recent experiments should be revised.
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Affiliation(s)
- F Leoni
- GIT-SPEC, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
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15
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Jana S, Singh JK, Kwak SK. Vapor-liquid critical and interfacial properties of square-well fluids in slit pores. J Chem Phys 2009; 130:214707. [DOI: 10.1063/1.3148884] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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16
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Morishige K. Hysteresis critical point of nitrogen in porous glass: occurrence of sample spanning transition in capillary condensation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:6221-6226. [PMID: 19466781 DOI: 10.1021/la900022s] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
To examine the mechanisms for capillary condensation and for capillary evaporation in porous glass, we measured the hysteresis critical points and desorption scanning curves of nitrogen in four kinds of porous glasses with different pore sizes (Vycor, CPG75A, CPG120A, and CPG170A). The shapes of the hysteresis loop in the adsorption isotherm of nitrogen for the Vycor and the CPG75A changed with temperature, whereas those for the CPG120A and the CPG170A remained almost unchanged with temperature. The hysteresis critical points for the Vycor and the CPG75A fell on the common line observed previously for ordered mesoporous silicas. On the other hand, the hysteresis critical points for the CPG120A and the CPG170A deviated appreciably from the common line. This strongly suggests that capillary evaporation of nitrogen in the interconnected and disordered pores of both the Vycor and the CPG75A follows a cavitation process at least in the vicinity of their hysteresis critical temperatures in the same way as that in the cagelike pores of the ordered silicas, whereas the hysteresis critical points in the CPG120A and the CPG170A have origin different from that in the cagelike pores. The desorption scanning curves for the CPG75A indicated the nonindependence of the porous domains. On the other hand, for both the CPG120A and the CPG170A, we obtained the scanning curves that are expected from the independent domain theory. All these results suggest that sample spanning transitions in capillary condensation and evaporation take place inside the interconnected pores of both the CPG120A and the CPG170A.
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Affiliation(s)
- Kunimitsu Morishige
- Department of Chemistry, Okayama University of Science, 1-1 Ridai-cho, Okayama 700-0005, Japan
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17
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Bhattacharya S, Coasne B, Hung FR, Gubbins KE. Modeling micelle-templated mesoporous material SBA-15: atomistic model and gas adsorption studies. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:5802-5813. [PMID: 19099416 DOI: 10.1021/la801560e] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We report the development of a realistic molecular model for mesoporous silica SBA-15, which includes both the large cylindrical mesopores and the smaller micropores in the pore walls. The methodology for modeling the SBA-15 structure involves molecular and mesoscale simulations combined with geometrical interpolation techniques. First, a mesoscale model is prepared by mimicking the synthesis process using lattice Monte Carlo simulations. The main physical features of this mesoscale pore model are then carved out of an atomistic silica block; both the mesopores and the micropores are incorporated from the mimetic simulations. The calculated pore size distribution, surface area, and simulated TEM images of the model structure are in good agreement with those obtained from experimental samples of SBA-15. We then investigate the adsorption of argon in this structure using Grand Canonical Monte Carlo (GCMC) simulations. The adsorption results for our SBA-15 model are compared with those for a similar model that does not include the micropores; we also compare with results obtained in a regular cylindrical pore. The simulated adsorption isotherm for the SBA-15 model shows semiquantitative agreement with the experimental isotherm for a SBA-15 sample having a similar pore size. We observe that the presence of the micropores leads to increased adsorption at low pressure compared to the case of a model without micropores in the pore walls. At higher pressures, for all models, the filling proceeds via the monolayer-multilayer adsorption on the mesopore surface followed by capillary condensation, which is mainly controlled by the mesopore diameter and is not influenced by the presence of the micropores.
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Affiliation(s)
- Supriyo Bhattacharya
- Center for High Performance Computing and Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695-7905, USA
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18
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Schmidt M. Test particle limit for the pair structure of quenched-annealed fluid mixtures. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 79:031405. [PMID: 19391942 DOI: 10.1103/physreve.79.031405] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2008] [Revised: 02/23/2009] [Indexed: 05/27/2023]
Abstract
A density functional route to the pair structure of quenched-annealed fluid mixtures is presented. The bulk two-body partial pair correlation functions of the mixture are identified with the one-body density distributions in an external potential that models a fixed test particle. Quenched-annealed (replica) density functional theory is used to calculate the inhomogeneous one-body density distributions. A closed theory is obtained by using an exact sum rule that equates two different expressions for the cross pair correlation function between unlike species. Results for binary quenched-annealed hard sphere mixtures are found to agree well with computer simulation data, improving over results from the replica Ornstein-Zernike equations using the direct correlation functions, obtained as second functional derivatives of the quenched-annealed excess free energy functional, as input. The proposed framework allows for the independent determination of the blocked part of the fluid-fluid partial pair correlation function.
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Affiliation(s)
- Matthias Schmidt
- Theoretische Physik II, Universität Bayreuth, D-95440 Bayreuth, Germany and H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom
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19
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Pellenq RJM, Coasne B, Denoyel RO, Coussy O. Simple phenomenological model for phase transitions in confined geometry. 2. Capillary condensation/evaporation in cylindrical mesopores. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:1393-1402. [PMID: 19138076 DOI: 10.1021/la8020244] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A simple phenomenological model that describes capillary condensation and evaporation of pure fluids confined in cylindrical mesopores is presented. Following the work of Celestini (Celestini, F. Phys. Lett. A 1997, 228, 84), the free energy density of the system is derived using interfacial tensions and a corrective term that accounts for the interaction coupling between the vapor/adsorbed liquid and the adsorbed liquid/adsorbent interfaces. This corrective term is shown to be consistent with the Gibbs adsorption isotherm and assessed by standard adsorption tests. This model reveals that capillary condensation and evaporation are metastable and equilibrium processes, respectively, hence exhibiting the existence of a hysteresis loop inadsorption/desorption isotherm that is well-known in experiment. We extend the phenomenological model of Celestini to give a quantitative description of adsorption on the pore wall and hysteresis width evolution with temperature and confinement. Direct quantitative comparison is made with experimental data for confined argon. Used as a characterizing tool, this integrated model allows in a single fit of an experimental adsorption/desorption isotherm assessing essential characterization data such as the specific surface area, pore volume, and mean pore size.
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Affiliation(s)
- Roland J-M Pellenq
- Centre Interdisciplinaire des Nanosciences de Marseille, CINaM, UPR CNRS 3118, Campus de Luminy, 13288 Marseille Cedex 09, France.
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Siderius DW, Gelb LD. Predicting gas adsorption in complex microporous and mesoporous materials using a new density functional theory of finely discretized lattice fluids. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:1296-1299. [PMID: 19123796 DOI: 10.1021/la803666t] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We introduce a nonlocal on-lattice version of density functional theory (DFT) that allows for efficient modeling of fluids in complex inhomogeneous materials. In its previous implementations, classical DFT has required fine discretization of the fluid density. As a result, in studies of gas adsorption it has been used only in idealized pore models with high symmetry. Our new lattice DFT dramatically reduces the computational demand required to model simple fluids and hence can be efficiently applied to complex materials with multiple directions of asymmetry. We apply our new lattice DFT to study nitrogen adsorption in a slit pore with open ends and directly obtain the correct desorption hysteresis. We also apply our DFT to predict hydrogen adsorption accurately in an atomistic model of a metal-organic framework.
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Affiliation(s)
- Daniel W Siderius
- Department of Chemistry and Center for Materials Innovation, Washington University in St Louis, St. Louis, Missouri 63130, USA
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21
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Wolf PE, Bonnet F, Guyon L, Lambert T, Perraud S, Puech L, Rousset B, Thibault P. Probing helium interfaces with light scattering: from fluid mechanics to statistical physics. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2009; 28:183-198. [PMID: 19139943 DOI: 10.1140/epje/i2008-10417-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2008] [Revised: 10/11/2008] [Accepted: 12/09/2008] [Indexed: 05/27/2023]
Abstract
We have investigated the formation of helium droplets in two physical situations. In the first one, droplets are atomised from superfluid or normal liquid by a fast helium vapour flow. In the second, droplets of normal liquid are formed inside porous glasses during the process of helium condensation. The context, aims, and results of these experiments are reviewed, with focus on the specificity of light scattering by helium. In particular, we discuss how, for different reasons, the closeness to unity of the index of refraction of helium allows in both cases to minimise the problem of multiple scattering and obtain results which it would not be possible to get using other fluids.
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Affiliation(s)
- P E Wolf
- Institut Néel, CNRS-UJF, BP 166, 38042 Grenoble-Cedex 9, France.
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22
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Nomura R, Osawa A, Mimori T, Ueno KI, Kato H, Okuda Y. Competition between thermal fluctuations and disorder in the crystallization of 4He in aerogel. PHYSICAL REVIEW LETTERS 2008; 101:175703. [PMID: 18999765 DOI: 10.1103/physrevlett.101.175703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2008] [Revised: 09/03/2008] [Indexed: 05/27/2023]
Abstract
The dynamical transition in the crystallization of 4He in aerogel has been investigated by direct visualization and dynamical phase diagrams have been determined. The crystal-superfluid interface in aerogel advances via creep at high temperatures and avalanches at low temperatures. The transition temperature is higher at a higher interface velocity and lower in higher porosity aerogels. The transition is due to competition between thermal fluctuations and disorder for the crystallization process.
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Affiliation(s)
- Ryuji Nomura
- Department of Condensed Matter Physics, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro, Tokyo, Japan
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23
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Coleman SW, Vassilicos JC. Tortuosity of unsaturated porous fractal materials. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 78:016308. [PMID: 18764051 DOI: 10.1103/physreve.78.016308] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2007] [Indexed: 05/26/2023]
Abstract
The tortuosity of a capillary-condensed film of inviscid fluid adsorbed onto fractal substrates as a function of the filling fraction of the fluid has been calculated numerically. This acts as a way of probing the multiscale structure of the objects. It is found that the variation of tortuosity alpha with filling fraction varphi is found to follow a power law of the form alpha approximately varphi- for both deterministic and stochastic fractals. These numerically calculated exponents are compared to exponents obtained from a phenomenological scaling and good agreement is found, particularly for the stochastic fractals.
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Affiliation(s)
- S W Coleman
- Department of Aeronautics and Institute for Mathematical Sciences, Imperial College, London, SW7 2BY, United Kingdom.
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24
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Hung FR, Bhattacharya S, Coasne B, Thommes M, Gubbins KE. Argon and krypton adsorption on templated mesoporous silicas: molecular simulation and experiment. ADSORPTION 2007. [DOI: 10.1007/s10450-007-9034-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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25
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Lurio LB, Mulders N, Paetkau M, Chan MHW, Mochrie SGJ. Small-angle x-ray scattering measurements of the microstructure of liquid helium mixtures adsorbed in aerogel. Phys Rev E 2007; 76:011506. [PMID: 17677449 DOI: 10.1103/physreve.76.011506] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2006] [Indexed: 11/07/2022]
Abstract
Small-angle x-ray scattering (SAXS) was used to measure the microstructure of isotopic mixtures of 3He and 4He adsorbed into silica aerogels as a function of temperature and 3He concentration. The SAXS measurements could be well described by the formation of a nearly pure film of 4He which separates from the bulk mixture onto the aerogel strands and which thickens with decreasing temperature. Previous observations of a superfluid 3He -rich phase are consistent with superfluidity existing within this film phase. Observed differences between different density aerogels are explained in terms of the depletion of 4He from the bulk mixture due to film formation.
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Affiliation(s)
- L B Lurio
- Department of Physics, Northern Illinois University, DeKalb, Illinois 60115, USA
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26
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Hung FR, Coasne B, Gubbins KE, Siperstein FR, Thommes M, Sliwinska-Bartkowiak M. A Monte Carlo study of capillary condensation of krypton within realistic models of templated mesoporous silica materials. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/s0167-2991(07)80021-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
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27
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Pellenq RM, Coasne B, Denoyel R, Puibasset J. Effect of pore morphology and topology on capillary condensation in nanopores: a theoretical and molecular simulation study. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/s0167-2991(07)80002-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/07/2023]
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28
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Detcheverry F, Kierlik E, Rosinberg ML, Tarjus G. Gas adsorption and desorption in silica aerogels: a theoretical study of scattering properties. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2006; 73:041511. [PMID: 16711813 DOI: 10.1103/physreve.73.041511] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2005] [Indexed: 05/09/2023]
Abstract
We present a numerical study of the structural correlations associated with gas adsorption and desorption in silica aerogels in order to provide a theoretical interpretation of scattering experiments. Following our earlier work, we use a coarse-grained lattice-gas description and determine the nonequilibrium behavior of the adsorbed gas within a local mean-field analysis. We focus on the differences between the adsorption and desorption mechanisms and their signature in the fluid-fluid and gel-fluid structure factors as a function of temperature. At low temperature, but still in the regime where the isotherms are continuous, we find that the adsorbed fluid density, during both filling and draining, is correlated over distances that may be much larger than the gel correlation length. In particular, extended fractal correlations may occur during desorption, indicating the existence of a ramified cluster of vapor filled cavities. This also induces an important increase of the scattering intensity at small wave vectors. The similarity and differences with the scattering of fluids in other porous solids such as Vycor are discussed.
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Affiliation(s)
- F Detcheverry
- Laboratoire de Physique Théorique de la Matière Condensée, Université Pierre et Marie Curie, 4 Place Jussieu, 75252 Paris Cedex 05, France
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29
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Müller M, Silva A. Instanton analysis of hysteresis in the three-dimensional random-field Ising model. PHYSICAL REVIEW LETTERS 2006; 96:117202. [PMID: 16605858 DOI: 10.1103/physrevlett.96.117202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Revised: 11/22/2005] [Indexed: 05/08/2023]
Abstract
We study the magnetic hysteresis in the random-field Ising model in 3D. We discuss the disorder dependence of the coercive field Hc, and obtain an analytical description of the smooth part of the hysteresis below and above Hc, by identifying the disorder configurations (instantons) that are the most probable to trigger local avalanches. We estimate the critical disorder strength at which the hysteresis curve becomes continuous. From an instanton analysis at zero field we obtain a description of local two-level systems in the ferromagnetic phase.
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Affiliation(s)
- Markus Müller
- Department of Physics, Rutgers University, Piscataway, New Jersey 08854, USA
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30
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Nomura R, Miyashita W, Yoneyama K, Okuda Y. Dynamics of capillary condensation in aerogels. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2006; 73:032601. [PMID: 16605581 DOI: 10.1103/physreve.73.032601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2005] [Revised: 01/24/2006] [Indexed: 05/08/2023]
Abstract
Dynamics of capillary condensation of liquid 4He in various density silica aerogels was investigated systematically. Interfaces were clearly visible when bulk liquid was rapidly sucked into the aerogel. Time evolution of the interface positions was consistent with the Washburn model and their effective pore radii were obtained. Condensation was a single step in a dense aerogel and two steps in a low density aerogel. Crossover between the two types of condensation was observed in an intermediate density aerogel. Variety of the dynamics may be the manifestation of the fractal nature of aerogels which had a wide range of distribution of pore radii.
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Affiliation(s)
- R Nomura
- Department of Condensed Matter Physics, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro, Tokyo 152-8551, Japan
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31
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Coasne B, Hung FR, Pellenq RJM, Siperstein FR, Gubbins KE. Adsorption of simple gases in MCM-41 materials: the role of surface roughness. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:194-202. [PMID: 16378420 DOI: 10.1021/la051676g] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
This paper reports the development and testing of atomistic models of silica MCM-41 pores. Model A is a regular cylindrical pore having a constant section. Model B has a surface disorder that reproduces the morphological features of a pore obtained from an on-lattice simulation that mimics the synthesis process of MCM-41 materials. Both models are generated using a similar procedure, which consists of carving the pore out of an atomistic silica block. The differences between the two models are analyzed in terms of small angle neutron scattering spectra as well as adsorption isotherms and isosteric heat curves for Ar at 87 K and Xe at 195 K. As expected for capillary condensation in regular nanopores, the Ar and Xe adsorption/desorption cycles for model A exhibit a large hysteresis loop having a symmetrical shape, i.e., with parallel adsorption and desorption branches. The features of the adsorption isotherms for model B strongly depart from those observed for model A. Both the Ar and Xe adsorption branches for model B correspond to a quasicontinuous pore filling that involves coexistence within the pore of liquid bridges and gas nanobubbles. As in the case of model A, the Ar adsorption isotherm for model B exhibits a significant hysteresis loop; however, the shape of the loop is asymmetrical with a desorption branch much steeper than the adsorption branch. In contrast, the adsorption/desorption cycle for Xe in model B is quasicontinuous and quasireversible. Comparison with adsorption and neutron scattering experiments suggests that model B is too rough at the molecular scale but reproduces reasonably the surface disorder of real MCM-41 at larger length scales. In contrast, model A is smooth at small length scales in agreement with experiments but seems to be too ordered at larger length scales.
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Affiliation(s)
- Benoit Coasne
- Center for High Performance Simulation, Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695-7905, USA.
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32
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Archer AJ, Schmidt M, Evans R. Soft core fluid in a quenched matrix of soft core particles: a mobile mixture in a model gel. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2006; 73:011506. [PMID: 16486153 DOI: 10.1103/physreve.73.011506] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2005] [Indexed: 05/06/2023]
Abstract
We present a density-functional study of a binary phase-separating mixture of soft core particles immersed in a random matrix of quenched soft core particles of larger size. This is a model for a binary polymer mixture immersed in a cross-linked rigid polymer network. Using the replica "trick" for quenched-annealed mixtures we derive an explicit density functional theory that treats the quenched species on the level of its one-body density distribution. The relation to a set of effective external potentials acting on the annealed components is discussed. We relate matrix-induced condensation in bulk to the behavior of the mixture around a single large particle. The interfacial properties of the binary mixture at a surface of the quenched matrix display a rich interplay between capillary condensation inside the bulk matrix and wetting phenomena at the matrix surface.
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Affiliation(s)
- A J Archer
- H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom.
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33
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Detcheverry F, Kierlik E, Rosinberg ML, Tarjus G. Helium condensation in aerogel: avalanches and disorder-induced phase transition. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 72:051506. [PMID: 16383610 DOI: 10.1103/physreve.72.051506] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2005] [Indexed: 05/05/2023]
Abstract
We present a detailed numerical study of the elementary condensation events (avalanches) associated to the adsorption of in silica aerogels. We use a coarse-grained lattice-gas description and determine the nonequilibrium behavior of the adsorbed gas within a local mean-field analysis, neglecting thermal fluctuations and activated processes. We investigate the statistical properties of the avalanches, such as their number, size and shape along the adsorption isotherms as a function of gel porosity, temperature, and chemical potential. Our calculations predict the existence of a line of critical points in the temperature-porosity diagram where the avalanche size distribution displays a power-law behavior and the adsorption isotherms have a universal scaling form. The estimated critical exponents seem compatible with those of the field-driven random field Ising model at zero temperature.
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Affiliation(s)
- F Detcheverry
- Laboratoire de Physique Théorique de la Matière Condensée, Université Pierre et Marie Curie, 4 place Jussieu, 75252 Paris Cedex 05, France
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34
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Cuesta JA, Lafuente L, Schmidt M. Lattice density functional for colloid-polymer mixtures: comparison of two fundamental measure theories. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 72:031405. [PMID: 16241433 DOI: 10.1103/physreve.72.031405] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2005] [Indexed: 05/05/2023]
Abstract
We consider a binary mixture of colloid and polymer particles with positions on a simple cubic lattice. Colloids exclude both colloids and polymers from nearest neighbor sites. Polymers are treated as effective particles that are mutually noninteracting, but exclude colloids from neighboring sites; this is a discrete version of the (continuum) Asakura-Oosawa-Vrij model. Two alternative density functionals are proposed and compared in detail. The first is based on multioccupancy in the zero-dimensional limit of the bare model, analogous to the corresponding continuum theory that reproduces the bulk fluid free energy of free volume theory. The second is based on mapping the polymers onto a multicomponent mixture of polymer clusters that are shown to behave as hard cores; the corresponding property of the extended model in strong confinement permits direct treatment with lattice fundamental measure theory. Both theories predict the same topology for the phase diagram with a continuous fluid-fcc freezing transition at low polymer fugacity and, upon crossing a tricritical point, a first-order freezing transition for high polymer fugacities with rapidly broadening density jump.
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Affiliation(s)
- José A Cuesta
- Grupo Interdisciplinar de Sistemas Complejos, Departamento de Matemáticas, Universidad Carlos III de Madrid, Avenida de la Universidad 30, E-28911 Leganés, Madrid, Spain
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35
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Adsorption in Controlled-Pore Glasses: Comparison of Molecular Simulations with a Mean-Field Lattice Gas Model. ADSORPTION 2005. [DOI: 10.1007/s10450-005-5938-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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36
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The Physics of Capillary Condensation in Disordered Mesoporous Materials: A Unifying Theoretical Description. ADSORPTION 2005. [DOI: 10.1007/s10450-005-5908-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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37
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Salazar R, Gelb LD. Application of the Bethe-Peierls approximation to a lattice-gas model of adsorption on mesoporous materials. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 71:041502. [PMID: 15903672 DOI: 10.1103/physreve.71.041502] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2004] [Indexed: 05/02/2023]
Abstract
We calculate adsorption and desorption isotherms in models of several classes of porous materials using a lattice-gas model solved in the Bethe-Peierls (quasichemical) approximation. Isotherms and fluid density profiles from the Bethe-Peierls and Bragg-Williams approximations are compared with grand-canonical Monte Carlo simulation results. The Bethe-Peierls approximation produces both more accurate adsorption and desorption isotherms and more realistic fluid density profiles than the Bragg-Williams approximation. Details of the application of the Bethe-Peierls approximation applied to a three-dimensionally inhomogeneous system are given. We show that the numerical solution of this theory can be accomplished using a self-consistent iterator very similar to that currently used in studies employing the Bragg-Williams approximation. This iterative scheme is substantially more efficient than the numerical optimization method used in many previous studies of lattice-gas models in the quasichemical approximation. We find that use of the Bethe-Peierls approximation is only slightly more computationally demanding than the Bragg-Williams approximation, and thus recommend it for use in future work on this class of models.
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Affiliation(s)
- Rafael Salazar
- Department of Chemistry and Center for Materials Innovation, Washington University in St. Louis, St. Louis, Missouri 63130, USA
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38
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Puibasset J. Thermodynamic Characterization of Fluids Confined in Heterogeneous Pores by Monte Carlo Simulations in the Grand Canonical and the Isobaric−Isothermal Ensembles. J Phys Chem B 2005; 109:8185-94. [PMID: 16851957 DOI: 10.1021/jp0502151] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Materials presenting nanoscale porosity are able to condense gases in their structure. This "capillary condensation" phenomenon has been studied for more than one century. Theoretical models help to understand experimental results but fail in explaining all experimental features. Most of the time, the difficulties in making quantitative or even qualitative predictions are due to the geometric complexity of the porous materials, such as large pore size distribution, chemical heterogeneities, or pore interconnections. Numerical calculations (lattice gas models or molecular simulations) are of considerable interest to calculate the adsorption properties of a fluid confined in a porous model with characteristic sizes up to several tens of nanometers. For instance, the grand canonical Monte Carlo method allows one to compute the average amount of fluid adsorbed in the porous model as a function of the temperature and the chemical potential of the fluid. However, the grand potential, necessary for a complete characterization of the system, is not a direct output of the algorithm. It is shown in this paper that the use of the isobaric-isothermal (NPT) ensemble allows one to circumvent this problem; that is, it is possible to get in one single Monte Carlo run the absolute grand potential for any given thermodynamic state of the fluid. A simplified thermodynamic integration scheme is then used to evaluate the grand potential over the whole isotherm branch passing through this initially given point. Since the usual NPT technique is a priori limited to homogeneous pores, it is proposed, for the first time, to generalize this procedure to a pore presenting a chemical heterogeneity along its axis. The new method gives the same results as the previous for homogeneous pores and allows new predictions for chemically heterogeneous pores. Comparison with the full integration scheme shows that the proposed direct calculation is faster since it avoids multiple Monte Carlo runs and more precise because it avoids the possible cumulative errors of the integration procedure.
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Affiliation(s)
- Joël Puibasset
- Centre de Recherche sur la Matière Divisée, CNRS-Université d'Orléans, 1b, rue de la Férollerie, 45071 Orléans Cedex 02, France.
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Duda Y, Pizio O, Sokolowski S. Nonadditive Binary Hard Sphere Mixture in Disordered Hard Sphere Matrices: Integral Equations and Computer Simulation. J Phys Chem B 2004. [DOI: 10.1021/jp040340x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Y. Duda
- Instituto Mexicano de Petroleo, Mexico D.F., Mexico, Institute of Condensed Matter Physics, National Academy of Sciences, Lviv, Ukraine, Instituto de Quimica de la UNAM, Coyoacan 04510, Mexico, D.F., and Department for the Modeling of Physico-Chemical Processes, Maria Curie-Skłodowska University, Lublin, Poland
| | - O. Pizio
- Instituto Mexicano de Petroleo, Mexico D.F., Mexico, Institute of Condensed Matter Physics, National Academy of Sciences, Lviv, Ukraine, Instituto de Quimica de la UNAM, Coyoacan 04510, Mexico, D.F., and Department for the Modeling of Physico-Chemical Processes, Maria Curie-Skłodowska University, Lublin, Poland
| | - S. Sokolowski
- Instituto Mexicano de Petroleo, Mexico D.F., Mexico, Institute of Condensed Matter Physics, National Academy of Sciences, Lviv, Ukraine, Instituto de Quimica de la UNAM, Coyoacan 04510, Mexico, D.F., and Department for the Modeling of Physico-Chemical Processes, Maria Curie-Skłodowska University, Lublin, Poland
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40
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Detcheverry F, Kierlik E, Rosinberg ML, Tarjus G. Mechanisms for gas adsorption and desorption in silica aerogels: the effect of temperature. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2004; 20:8006-8014. [PMID: 15350065 DOI: 10.1021/la0488506] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We present a theoretical study of the adsorption and desorption mechanisms of fluids in silica aerogels, focusing on the effect of temperature. We adopt a coarse-grained lattice description in which the gel structure is generated by a diffusion-limited cluster-cluster aggregation algorithm and the fluid configurations are computed using local mean-field (i.e., density functional) theory. Our calculations reproduce qualitatively the changes in the shape of the hysteresis loops observed with (4)He in gels of varying porosity. We study in detail the morphology of the condensation and evaporation events that correspond to the irreversible processes (avalanches) which are at the origin of the hysteresis. Depending on porosity and temperature, these avalanches may be localized, involve regions that extend beyond the gel correlation length, or even span the entire sample. This makes difficult the characterization of aerogels based on analyzing sorption isotherms.
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Affiliation(s)
- F Detcheverry
- Laboratoire de Physique Théorique des Liquides, Université Pierre et Marie Curie, 4 place Jussieu, 75252 Paris Cedex 05, France
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41
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Salazar R, Gelb * LD. An investigation of the effects of the structure of gel materials on their adsorptive properties using a simple lattice–gas model. Mol Phys 2004. [DOI: 10.1080/00268970410001726854] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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