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Bartsch H, Bier M, Dietrich S. Interface structures in ionic liquid crystals. SOFT MATTER 2019; 15:4109-4126. [PMID: 31080982 DOI: 10.1039/c9sm00062c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Ionic liquid crystals (ILCs) are anisotropic mesogenic molecules which additionally carry charges. This combination gives rise to a complex interplay of the underlying (anisotropic) contributions to the pair interactions. It promises interesting and distinctive structural and orientational properties to arise in systems of ILCs, combining properties of liquid crystals and ionic liquids. While previous theoretical studies have focused on the phase behavior of ILCs and the structure of the respective bulk phases, in the present study we provide new results, obtained within density functional theory, concerning (planar) free interfaces between an isotropic liquid L and two types of smectic-A phases (SA or SAW). We discuss the structural and orientational properties of these interfaces in terms of the packing fraction profile η(r) and the orientational order parameter profile S2(r) concerning the tilt angle α between the (bulk) smectic layer normal and the interface normal. The asymptotic decay of η(r) and of S2(r) towards their values in the isotropic bulk is discussed, too.
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Affiliation(s)
- Hendrik Bartsch
- Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, 70569, Stuttgart, Germany.
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2
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Farhan A, Saccone M, Petersen CF, Dhuey S, Chopdekar RV, Huang YL, Kent N, Chen Z, Alava MJ, Lippert T, Scholl A, van Dijken S. Emergent magnetic monopole dynamics in macroscopically degenerate artificial spin ice. SCIENCE ADVANCES 2019; 5:eaav6380. [PMID: 30783629 PMCID: PMC6368442 DOI: 10.1126/sciadv.aav6380] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 12/21/2018] [Indexed: 05/26/2023]
Abstract
Magnetic monopoles, proposed as elementary particles that act as isolated magnetic south and north poles, have long attracted research interest as magnetic analogs to electric charge. In solid-state physics, a classical analog to these elusive particles has emerged as topological excitations within pyrochlore spin ice systems. We present the first real-time imaging of emergent magnetic monopole motion in a macroscopically degenerate artificial spin ice system consisting of thermally activated Ising-type nanomagnets lithographically arranged onto a pre-etched silicon substrate. A real-space characterization of emergent magnetic monopoles within the framework of Debye-Hückel theory is performed, providing visual evidence that these topological defects act like a plasma of Coulomb-type magnetic charges. In contrast to vertex defects in a purely two-dimensional artificial square ice, magnetic monopoles are free to evolve within a divergence-free vacuum, a magnetic Coulomb phase, for which features in the form of pinch-point singularities in magnetic structure factors are observed.
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Affiliation(s)
- Alan Farhan
- Advanced Light Source, Lawrence Berkeley National Laboratory (LBNL), 1 Cyclotron Road, Berkeley, CA 94720, USA
- Laboratory for Multiscale Materials Experiments (LMX), Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Michael Saccone
- Physics Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA
| | - Charlotte F. Petersen
- COMP Centre of Excellence, Department of Applied Physics, Aalto University, P.O. Box 11100, FI-00076 Aalto, Espoo, Finland
- Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße 21A, A-6020 Innsbruck, Austria
| | - Scott Dhuey
- Molecular Foundry, LBNL, 1 Cyclotron Road, Berkeley, CA 94720, USA
| | - Rajesh V. Chopdekar
- Advanced Light Source, Lawrence Berkeley National Laboratory (LBNL), 1 Cyclotron Road, Berkeley, CA 94720, USA
| | - Yen-Lin Huang
- Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Noah Kent
- Physics Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA
- Materials Sciences Division, LBNL, 1 Cyclotron Road, Berkeley, CA 94720, USA
| | - Zuhuang Chen
- School of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen, Guangdong 518055, China
| | - Mikko J. Alava
- COMP Centre of Excellence, Department of Applied Physics, Aalto University, P.O. Box 11100, FI-00076 Aalto, Espoo, Finland
| | - Thomas Lippert
- Laboratory for Multiscale Materials Experiments (LMX), Paul Scherrer Institute, 5232 Villigen, Switzerland
- Department of Chemistry and Applied Biosciences, Laboratory of Inorganic Chemistry, ETH Zurich, Switzerland
| | - Andreas Scholl
- Advanced Light Source, Lawrence Berkeley National Laboratory (LBNL), 1 Cyclotron Road, Berkeley, CA 94720, USA
| | - Sebastiaan van Dijken
- NanoSpin, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto, Finland
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3
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Girotto M, Dos Santos AP, Levin Y. Simulations of ionic liquids confined by metal electrodes using periodic Green functions. J Chem Phys 2018; 147:074109. [PMID: 28830185 DOI: 10.1063/1.4989388] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
We present an efficient method for simulating Coulomb systems confined by metal electrodes. The approach relies on Green function techniques to obtain the electrostatic potential for an infinite periodically replicated system. This avoids the use of image charges or an explicit calculation of the induced surface charge, both of which dramatically slows down the simulations. To demonstrate the utility of the new method, we use it to obtain the ionic density profiles and the differential capacitances, which are of great practical and theoretical interest, for a lattice model of an ionic liquid.
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Affiliation(s)
- Matheus Girotto
- Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970 Porto Alegre, RS, Brazil
| | - Alexandre P Dos Santos
- Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970 Porto Alegre, RS, Brazil
| | - Yan Levin
- Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970 Porto Alegre, RS, Brazil
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Girotto M, Colla T, Dos Santos AP, Levin Y. Lattice Model of an Ionic Liquid at an Electrified Interface. J Phys Chem B 2017; 121:6408-6415. [PMID: 28590756 DOI: 10.1021/acs.jpcb.7b02258] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We study ionic liquids interacting with electrified interfaces. The ionic fluid is modeled as a Coulomb lattice gas. We compare the ionic density profiles calculated using a popular modified Poisson-Boltzmann equation with the explicit Monte Carlo simulations. The modified Poisson-Boltzmann theory fails to capture the structural features of the double layer and is also unable to correctly predict the ionic density at the electrified interface. The lattice Monte Carlo simulations qualitatively capture the coarse-grained structure of the double layer in the continuum. We propose a convolution relation that semiquantitatively relates the ionic density profiles of a continuum ionic liquid and its lattice counterpart near an electrified interface.
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Affiliation(s)
- Matheus Girotto
- Instituto de Física, Universidade Federal do Rio Grande do Sul , Caixa Postal 15051, CEP 91501-970, Porto Alegre, RS Brazil
| | - Thiago Colla
- Instituto de Física, Universidade Federal de Ouro Preto , CEP 35400-000, Ouro Preto, MG Brazil
| | - Alexandre P Dos Santos
- Instituto de Física, Universidade Federal do Rio Grande do Sul , Caixa Postal 15051, CEP 91501-970, Porto Alegre, RS Brazil
| | - Yan Levin
- Instituto de Física, Universidade Federal do Rio Grande do Sul , Caixa Postal 15051, CEP 91501-970, Porto Alegre, RS Brazil
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6
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Magnetic-charge ordering and phase transitions in monopole-conserved square spin ice. Sci Rep 2015; 5:15875. [PMID: 26511870 PMCID: PMC4625371 DOI: 10.1038/srep15875] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 10/06/2015] [Indexed: 11/16/2022] Open
Abstract
Magnetic-charge ordering and corresponding magnetic/monopole phase transitions in spin ices are the emergent topics of condensed matter physics. In this work, we investigate a series of magnetic-charge (monopole) phase transitions in artificial square spin ice model using the conserved monopole density algorithm. It is revealed that the dynamics of low monopole density lattices is controlled by the effective Coulomb interaction and the Dirac string tension, leading to the monopole dimerization which is quite different from the dynamics of three-dimensional pyrochlore spin ice. The condensation of the monopole dimers into monopole crystals with staggered magnetic-charge order can be predicted clearly. For the high monopole density cases, the lattice undergoes two consecutive phase transitions from high-temperature paramagnetic/charge-disordered phase into staggered charge-ordered phase before eventually toward the long-range magnetically-ordered phase as the ground state which is of staggered charge order too. A phase diagram over the whole temperature-monopole density space, which exhibits a series of emergent spin and monopole ordered states, is presented.
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Kaiser V, Bramwell ST, Holdsworth PCW, Moessner R. ac Wien Effect in Spin Ice, Manifest in Nonlinear, Nonequilibrium Susceptibility. PHYSICAL REVIEW LETTERS 2015; 115:037201. [PMID: 26230822 DOI: 10.1103/physrevlett.115.037201] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Indexed: 06/04/2023]
Abstract
The Wien effect is a model process for field-induced charge creation. Here it is derived for a nonelectrical system: the spin ice "magnetolyte"-a unique system showing perfect charge symmetry. An entropic reaction field, analogous to the Jaccard field in ice, opposes direct current, but a frequency window exists in which the Wien effect for magnetolyte and electrolyte are indistinguishable. The universal enhancement of monopole density speeds up the magnetization dynamics, which manifests in the nonlinear, nonequilibrium ac susceptibility. This is a rare instance where such effects may be calculated, providing new insights for electrolytes. Experimental predictions are made for Dy2Ti2O7 spin ice.
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Affiliation(s)
- V Kaiser
- Laboratoire de Physique, École Normale Supérieure de Lyon, CNRS, 69364 Lyon CEDEX 07, France
- Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden, Germany
| | - S T Bramwell
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London WC1H 0AH, United Kingdom
| | - P C W Holdsworth
- Laboratoire de Physique, École Normale Supérieure de Lyon, CNRS, 69364 Lyon CEDEX 07, France
| | - R Moessner
- Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden, Germany
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8
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Bartsch H, Dannenmann O, Bier M. Thermal and structural properties of ionic fluids. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 91:042146. [PMID: 25974477 DOI: 10.1103/physreve.91.042146] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Indexed: 06/04/2023]
Abstract
The electrostatic interaction in ionic fluids is well known to give rise to a characteristic phase behavior and structure. Sometimes its long range is proposed to single out the electrostatic potential over other interactions with shorter ranges. Here the importance of the range for the phase behavior and the structure of ionic fluids is investigated by means of grandcanonical Monte Carlo simulations of the lattice restricted primitive model (LRPM). The long-ranged electrostatic interaction is compared to various types of short-ranged potentials obtained by sharp and/or smooth cutoff schemes. Sharply cutoff electrostatic potentials are found to lead to a strong dependence of the phase behavior and the structure on the cutoff radius. However, when combined with a suitable additional smooth cutoff, the short-ranged LRPM is found to exhibit quantitatively the same phase behavior and structure as the conventional long-ranged LRPM. Moreover, the Stillinger-Lovett perfect screening property, which is well known to be generated by the long-ranged electrostatic potential, is also fulfilled by short-ranged LRPMs with smooth cutoffs. By showing that the characteristic phase behavior and structure of ionic fluids can also be found in systems with short-ranged potentials, one can conclude that the decisive property of the electrostatic potential in ionic fluids is not the long range but rather the valency dependence.
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Affiliation(s)
- Hendrik Bartsch
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, 70569 Stuttgart, Germany and Institut für Theoretische Physik IV, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
| | - Oliver Dannenmann
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, 70569 Stuttgart, Germany and Institut für Theoretische Physik IV, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
| | - Markus Bier
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, 70569 Stuttgart, Germany and Institut für Theoretische Physik IV, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
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9
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Démery V, Dean DS, Hammant TC, Horgan RR, Podgornik R. The one-dimensional Coulomb lattice fluid capacitor. J Chem Phys 2012; 137:064901. [PMID: 22897305 DOI: 10.1063/1.4740233] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The one-dimensional Coulomb lattice fluid in a capacitor configuration is studied. The model is formally exactly soluble via a transfer operator method within a field theoretic representation of the model. The only interactions present in the model are the one-dimensional Coulomb interaction between cations and anions and the steric interaction imposed by restricting the maximal occupancy at any lattice site to one particle. Despite the simplicity of the model, a wide range of intriguing physical phenomena arise, some of which are strongly reminiscent of those seen in experiments and numerical simulations of three-dimensional ionic liquid based capacitors. Notably, we find regimes where over-screening and density oscillations are seen near the capacitor plates. The capacitance is also shown to exhibit strong oscillations as a function of applied voltage. It is also shown that the corresponding mean-field theory misses most of these effects. The analytical results are confirmed by extensive numerical simulations.
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Affiliation(s)
- Vincent Démery
- Laboratoire de Physique Théorique (IRSAMC), Université de Toulouse, UPS and CNRS, F-31062 Toulouse, France
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10
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Zhou HD, Bramwell ST, Cheng JG, Wiebe CR, Li G, Balicas L, Bloxsom JA, Silverstein HJ, Zhou JS, Goodenough JB, Gardner JS. High pressure route to generate magnetic monopole dimers in spin ice. Nat Commun 2011; 2:478. [PMID: 21934662 PMCID: PMC3195216 DOI: 10.1038/ncomms1483] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Accepted: 08/17/2011] [Indexed: 11/09/2022] Open
Abstract
The gas of magnetic monopoles in spin ice is governed by one key parameter: the monopole chemical potential. A significant variation of this parameter could access hitherto undiscovered magnetic phenomena arising from monopole correlations, as observed in the analogous electrical Coulomb gas, like monopole dimerization, critical phase separation, or charge ordering. However, all known spin ices have values of chemical potential imposed by their structure and chemistry that place them deeply within the weakly correlated regime, where none of these interesting phenomena occur. Here we use high-pressure synthesis to create a new monopole host, Dy(2)Ge(2)O(7), with a radically altered chemical potential that stabilizes a large fraction of monopole dimers. The system is found to be ideally described by the classic Debye-Huckel-Bjerrum theory of charge correlations. We thus show how to tune the monopole chemical potential in spin ice and how to access the diverse collective properties of magnetic monopoles.
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Affiliation(s)
- H D Zhou
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, USA
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11
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Affiliation(s)
- Alberto Striolo
- School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, OK 73019, U.S.A
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12
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Mebane DS, Maier J. DC conductivity and dielectric properties in silver chloride, revisited. Phys Chem Chem Phys 2010; 12:2478-87. [DOI: 10.1039/b916791a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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13
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Varela LM, Carrete J, Turmine M, Rilo E, Cabeza O. Pseudolattice Theory of the Surface Tension of Ionic Liquid−Water Mixtures. J Phys Chem B 2009; 113:12500-5. [DOI: 10.1021/jp9057065] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- L. M. Varela
- Grupo de Nanomateriales y Materia Blanda, Departamento de Física de la Materia Condensada, Universidad de Santiago de Compostela, E-15782, Santiago de Compostela, Spain, Université Pierre et Marie Curie-PARIS6, Laboratoire Interfaces et Systèmes Electrochimiques, CNRS, UPR15-LISE, Paris, F-75005 France, and Facultad de Ciencias, Universidad de A Coruña, Campus A Zapateira s/n, E-15072, A Coruña, Spain
| | - J. Carrete
- Grupo de Nanomateriales y Materia Blanda, Departamento de Física de la Materia Condensada, Universidad de Santiago de Compostela, E-15782, Santiago de Compostela, Spain, Université Pierre et Marie Curie-PARIS6, Laboratoire Interfaces et Systèmes Electrochimiques, CNRS, UPR15-LISE, Paris, F-75005 France, and Facultad de Ciencias, Universidad de A Coruña, Campus A Zapateira s/n, E-15072, A Coruña, Spain
| | - M. Turmine
- Grupo de Nanomateriales y Materia Blanda, Departamento de Física de la Materia Condensada, Universidad de Santiago de Compostela, E-15782, Santiago de Compostela, Spain, Université Pierre et Marie Curie-PARIS6, Laboratoire Interfaces et Systèmes Electrochimiques, CNRS, UPR15-LISE, Paris, F-75005 France, and Facultad de Ciencias, Universidad de A Coruña, Campus A Zapateira s/n, E-15072, A Coruña, Spain
| | - E. Rilo
- Grupo de Nanomateriales y Materia Blanda, Departamento de Física de la Materia Condensada, Universidad de Santiago de Compostela, E-15782, Santiago de Compostela, Spain, Université Pierre et Marie Curie-PARIS6, Laboratoire Interfaces et Systèmes Electrochimiques, CNRS, UPR15-LISE, Paris, F-75005 France, and Facultad de Ciencias, Universidad de A Coruña, Campus A Zapateira s/n, E-15072, A Coruña, Spain
| | - O. Cabeza
- Grupo de Nanomateriales y Materia Blanda, Departamento de Física de la Materia Condensada, Universidad de Santiago de Compostela, E-15782, Santiago de Compostela, Spain, Université Pierre et Marie Curie-PARIS6, Laboratoire Interfaces et Systèmes Electrochimiques, CNRS, UPR15-LISE, Paris, F-75005 France, and Facultad de Ciencias, Universidad de A Coruña, Campus A Zapateira s/n, E-15072, A Coruña, Spain
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Castelnovo C, Moessner R, Sondhi SL. Magnetic monopoles in spin ice. Nature 2008; 451:42-5. [PMID: 18172493 DOI: 10.1038/nature06433] [Citation(s) in RCA: 332] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2007] [Accepted: 10/29/2007] [Indexed: 11/09/2022]
Abstract
Electrically charged particles, such as the electron, are ubiquitous. In contrast, no elementary particles with a net magnetic charge have ever been observed, despite intensive and prolonged searches (see ref. 1 for example). We pursue an alternative strategy, namely that of realizing them not as elementary but rather as emergent particles-that is, as manifestations of the correlations present in a strongly interacting many-body system. The most prominent examples of emergent quasiparticles are the ones with fractional electric charge e/3 in quantum Hall physics. Here we propose that magnetic monopoles emerge in a class of exotic magnets known collectively as spin ice: the dipole moment of the underlying electronic degrees of freedom fractionalises into monopoles. This would account for a mysterious phase transition observed experimentally in spin ice in a magnetic field, which is a liquid-gas transition of the magnetic monopoles. These monopoles can also be detected by other means, for example, in an experiment modelled after the Stanford magnetic monopole search.
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Affiliation(s)
- C Castelnovo
- Rudolf Peierls Centre for Theoretical Physics, Oxford University, Oxford OX1 3NP, UK.
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Gutkowski KI, Bianchi HL, Japas ML. Nonasymptotic Critical Behavior of a Ternary Ionic System. J Phys Chem B 2007; 111:2554-64. [PMID: 17302450 DOI: 10.1021/jp067069z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Refractive indices n and salt concentrations ms of coexisting phases of the ternary system 1,4-dioxane + water + potassium chloride were measured along the liquid-liquid-solid coexistence curve near the liquid-liquid critical end point. Refractive index measurements were carried out in the range 0.689 x 10-3 < t = (T - Tc)/Tc < 0.118 while salt concentrations were determined for the temperature range 1.84 x 10-3 < t < 8.07 x 10-2. From these experimental results, compositions fD (mass fraction of dioxane on a salt-free basis) and densities rho of coexisting phases were obtained. The shape of the coexistence curve was analyzed using alternatively n, ms, fD, and rho as order parameters. In all cases, the obtained coexistence curve displays, asymptotically, Ising behavior. Outside the asymptotic critical domain, n, ms, and rho show significant deviations of the effective critical exponent from its Ising value, while the concentration variable fD requires no corrections to simple scaling. On the basis of the present results, we conclude that this system shows no indication of multicritical behavior.
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Affiliation(s)
- Karin I Gutkowski
- Unidad de Actividad Química, Comisión Nacional de Energía Atómica, Av. del Libertador 8250, 1429 Buenos Aires, Argentina
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Ren R, O'Keeffe CJ, Orkoulas G. Simulation of symmetric tricritical behavior in electrolytes. J Chem Phys 2006; 125:124504. [PMID: 17014188 DOI: 10.1063/1.2354148] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Despite extensive experimental, theoretical, and simulation efforts, a unified description of ionic phase transitions and criticality has not yet emerged. In this work, we investigate the phase behavior of the restricted primitive model of electrolyte solutions on the simple cubic lattice using grand canonical Monte Carlo simulations and finite-size scaling techniques. The phase diagram of the system is distinctly different from its continuum-space analog. We find order-disorder transitions for reduced temperatures T* < or approximately 0.51, where the ordered structures resemble those of the NaCl crystal. The order-disorder transition is continuous for 0.15 < or approximately T* < or approximately 0.51 and becomes first order at lower temperatures. The line of first-order transitions is a line of three-phase coexistence between a disordered and two ordered phases. The line of continuous, second-order transitions meets this line of triple points at a tricritical point at T* approximately equal to 0.1475. We locate the line of continuous transitions, and the line of triple points using finite-size scaling techniques. The tricritical temperature is estimated by extrapolation of the size-dependent tricritical temperatures obtained from a sixth-order Landau expansion of the free energy. Our calculated phase diagram is in qualitative agreement with mean-field theories.
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Affiliation(s)
- Ruichao Ren
- Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, CA 90095, USA
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17
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Schröer W, Wagner M, Stanga O. Apparent mean-field criticality of liquid–liquid phase transitions in ionic solutions. J Mol Liq 2006. [DOI: 10.1016/j.molliq.2006.03.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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18
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Artyomov MN, Kolomeisky * AB. Thermodynamics and phase transitions of electrolytes on lattices with different discretization parameters. Mol Phys 2005. [DOI: 10.1080/00268970500142683] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Diehl A, Panagiotopoulos AZ. Phase diagrams in the lattice restricted primitive model: from order-disorder to gas-liquid phase transition. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 71:046118. [PMID: 15903737 DOI: 10.1103/physreve.71.046118] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2004] [Indexed: 05/02/2023]
Abstract
The phase behavior of the lattice restricted primitive model (RPM) for ionic systems with additional short-range nearest neighbor (NN) repulsive interactions has been studied by grand canonical Monte Carlo simulations. We obtain a rich phase behavior as the NN strength is varied. In particular, the phase diagram is very similar to that of the continuum RPM for high NN strength. Specifically, we have found both gas-liquid phase separation, with associated Ising critical point, and a first-order liquid-solid transition. We discuss how the line of continuous order-disorder transitions present for the low NN strength changes into continuum-space behavior as one increases the NN strength and compare our findings with recent theoretical results by Ciach and Stell [Phys. Rev. Lett. 91, 060601 (2003)].
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Affiliation(s)
- Alexandre Diehl
- Departamento de Física, Universidade Federal do Ceará, Caixa Postal 6030, CEP 60455-760, Fortaleza, Ceará, Brazil.
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20
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Ciach A. Effect of charge-density fluctuations on the order-disorder transition in the lattice restricted primitive models of electrolytes. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2004; 70:046103. [PMID: 15600456 DOI: 10.1103/physreve.70.046103] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2004] [Revised: 06/23/2004] [Indexed: 05/24/2023]
Abstract
Lattice restricted primitive models, where equally charged ions of a diameter sigma are located at sites of a simple cubic lattice with a lattice constant a , are studied within the field-theoretic approach. We focus on the transition between charge-disordered and charge-ordered phases for sigma/a=1 and sigma/a=2 . By using renormalization-group methods we show that at high concentrations of ions the transition is continuous for sigma/a=1 , while for sigma/a=2 it is only first order, as found previously in simulations. For sigma/a=1 the effect of charge-density fluctuations on the positions of the continuous transition and the tricritical point (TCP) is determined within a formalism developed in this work. The temperature and the concentration of ions at the TCP agree very well with simulation results.
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Affiliation(s)
- A Ciach
- Institute of Physical Chemistry, Polish Academy of Sciences, 01-224 Warszawa, Poland
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Ciach A, Stell G. Criticality, tricriticality, and crystallization in discretized models of electrolytes. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2004; 70:016114. [PMID: 15324136 DOI: 10.1103/physreve.70.016114] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2004] [Indexed: 05/24/2023]
Abstract
The Restricted Primitive Model of ionic systems is studied within a field-theoretic approach in order to provide a theoretic basis for the qualitative difference in the phase diagrams obtained in simulations for sigma/a=1,sigma/a=2, and sigma/a>/=3 ( a is the lattice constant and sigma is the ion diameter). The evolution of the phase diagrams from the case sigma/a=1 to the case sigma/a=square root[2] [nearest-neighbor ( NN ) occupancy excluded] is studied in the model with NN repulsion, 0</=J</= infinity, supplementing Coulomb forces. The boundary of stability of the charge-disordered phase with respect to short-wavelength charge fluctuations and the tricritical point are found in a mean-field ( MF ) approximation. Next, the effect of fluctuations is studied and we find that for J exceeding a particular value J0 a fluctuation-induced first-order phase transition should be expected instead of the continuous transition found in MF. At J= J0 the line of continuous transitions splits into two lines enclosing the two-phase region, whose thickness increases from zero when J>/= J0 increases. We argue that this transition corresponds to formation of a bcc ionic crystal. For high densities the ions form an fcc crystal, for which we find a fluctuation-induced first-order charge-ordered-charge-disordered transition, in agreement with recent simulation studies. Our results also shed light on the simulation results obtained for an off-lattice ionic system, for which a schematic phase diagram is constructed.
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Affiliation(s)
- A Ciach
- Institute of Physical Chemistry, Polish Academy of Sciences 01-224 Warszawa, Poland
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22
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Kobelev V, Kolomeisky AB, Panagiotopoulos AZ. Thermodynamics of electrolytes on anisotropic lattices. ACTA ACUST UNITED AC 2003; 68:066110. [PMID: 14754272 DOI: 10.1103/physreve.68.066110] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2003] [Indexed: 11/07/2022]
Abstract
The phase behavior of ionic fluids on simple cubic and tetragonal (anisotropic) lattices has been studied by grand canonical Monte Carlo simulations. Systems with both the true lattice Coulombic potential and continuous-space 1/r electrostatic interactions have been investigated. At all degrees of anisotropy, only coexistence between a disordered low-density phase and an ordered high-density phase with the structure similar to ionic crystal was found, in contrast to recent theoretical predictions. Tricritical parameters were determined to be increasing functions of anisotropy parameters which is consistent with theoretical calculations based on the Debye-Hückel approach. At large anisotropies a two-dimensional-like behavior is observed, from which we estimated the dimensionless tricritical temperature and density for the two-dimensional square lattice electrolyte to be T*(tri)=0.14 and rho*(tri)=0.70.
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Affiliation(s)
- Vladimir Kobelev
- Department of Chemistry, Rice University, Houston, Texas 77005, USA
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23
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Daub CD, Patey GN, Camp PJ. Liquid–vapor criticality in a fluid of charged hard dumbbells. J Chem Phys 2003. [DOI: 10.1063/1.1609192] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Ciach A, Stell G. Effect of space discretization on phase diagrams in ionic systems: a field-theoretic approach. PHYSICAL REVIEW LETTERS 2003; 91:060601. [PMID: 12935060 DOI: 10.1103/physrevlett.91.060601] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2003] [Indexed: 05/24/2023]
Abstract
Using Landau-Ginzburg-Wilson field-theoretic methods we determine for what kind of space discretization the transition between charge-disordered and charge-ordered phases in the restricted primitive model is fluctuation-induced first order. We identify this transition with ionic-crystal formation. We predict four types of generic phase diagrams in ionic systems for various kinds of space discretization for low and intermediate densities of ions. Our results also shed light on the simulation results obtained for an off-lattice ionic system over a wide range of densities, including the fcc crystal.
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Affiliation(s)
- A Ciach
- Institute of Physical Chemistry, Polish Academy of Sciences 01-224 Warszawa, Poland
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Vega C, Abascal JLF, McBride C, Bresme F. The fluid–solid equilibrium for a charged hard sphere model revisited. J Chem Phys 2003. [DOI: 10.1063/1.1576374] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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26
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Artyomov MN, Kobelev V, Kolomeisky AB. Lattice models of ionic systems with charge asymmetry. J Chem Phys 2003. [DOI: 10.1063/1.1558311] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Diehl A, Panagiotopoulos AZ. Phase transitions and tricriticality in the lattice restricted primitive model supplemented by short-range interactions. J Chem Phys 2003. [DOI: 10.1063/1.1545095] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Ciach A, Góźdź WT, Evans R. Effect of a nearby charge-ordered phase on correlation functions in ionic systems. J Chem Phys 2003. [DOI: 10.1063/1.1539046] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Orkoulas G, Kumar SK, Panagiotopoulos AZ. Monte carlo study of coulombic criticality in polyelectrolytes. PHYSICAL REVIEW LETTERS 2003; 90:048303. [PMID: 12570467 DOI: 10.1103/physrevlett.90.048303] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2002] [Indexed: 05/24/2023]
Abstract
The role of charges in determining the water solubility of polyelectrolytes, a question of considerable relevance to biology, is currently unresolved. We use computer simulations to study the purely Coulombic phase separation of flexible polyelectrolytes with monovalent counterions in an athermal solvent. In agreement with recent theories we find that the critical temperature for this transition increases with chain length, but that the critical density remains unchanged. We therefore stress that the phase behavior of polyelectrolytes is qualitatively different from uncharged polymers, where the critical density decreases towards zero for long chains.
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Affiliation(s)
- G Orkoulas
- Department of Chemical Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
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Gutkowski KI, Bianchi HL, Japas ML. Critical behavior of a ternary ionic system: A controversy. J Chem Phys 2003. [DOI: 10.1063/1.1536611] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Wagner M, Stanga O, Schröer W. Corresponding states analysis of the critical points in binary solutions of room temperature ionic liquids. Phys Chem Chem Phys 2003. [DOI: 10.1039/b305959f] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Wagner M, Stanga O, Schröer W. Tricriticality in the ternary system 3-methylpyridine/water/NaBr? Measurements of the viscosity. Phys Chem Chem Phys 2002. [DOI: 10.1039/b206974a] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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