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Biswas T, Kahl G, Shrivastav GP. Phase separation dynamics in a symmetric binary mixture of ultrasoft particles. J Chem Phys 2024; 160:214901. [PMID: 38828826 DOI: 10.1063/5.0209814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2024] [Accepted: 05/10/2024] [Indexed: 06/05/2024] Open
Abstract
Phase separation plays a key role in determining the self-assembly of biological and soft-matter systems. In biological systems, liquid-liquid phase separation inside a cell leads to the formation of various macromolecular aggregates. The interaction among these aggregates is soft, i.e., they can significantly overlap at a small energy cost. From a computer simulation point of view, these complex macromolecular aggregates are generally modeled by soft particles. The effective interaction between two particles is defined via the generalized exponential model of index n, with n = 4. Here, using molecular dynamics simulations, we study the phase separation dynamics of a size-symmetric binary mixture of ultrasoft particles. We find that when the mixture is quenched to a temperature below the critical temperature, the two components spontaneously start to separate. Domains of the two components form, and the equal-time order parameter reveals that the domain sizes grow with time in a power-law manner with an exponent of 1/3, which is consistent with the Lifshitz-Slyozov law for conserved systems. Furthermore, the static structure factor shows a power-law decay with an exponent of 4, consistent with the Porod law.
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Affiliation(s)
- Tanmay Biswas
- Institut für Theoretische Physik, TU Wien, Wiedner Hauptstrasse 8-10, A-1040 Wien, Austria
| | - Gerhard Kahl
- Institut für Theoretische Physik, TU Wien, Wiedner Hauptstrasse 8-10, A-1040 Wien, Austria
| | - Gaurav P Shrivastav
- Institut für Theoretische Physik, TU Wien, Wiedner Hauptstrasse 8-10, A-1040 Wien, Austria
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2
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Höfling F, Dietrich S. Structure of liquid-vapor interfaces: Perspectives from liquid state theory, large-scale simulations, and potential grazing-incidence x-ray diffraction. J Chem Phys 2024; 160:104107. [PMID: 38469908 DOI: 10.1063/5.0186955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Accepted: 02/15/2024] [Indexed: 03/13/2024] Open
Abstract
Grazing-incidence x-ray diffraction (GIXRD) is a scattering technique that allows one to characterize the structure of fluid interfaces down to the molecular scale, including the measurement of surface tension and interface roughness. However, the corresponding standard data analysis at nonzero wave numbers has been criticized as to be inconclusive because the scattering intensity is polluted by the unavoidable scattering from the bulk. Here, we overcome this ambiguity by proposing a physically consistent model of the bulk contribution based on a minimal set of assumptions of experimental relevance. To this end, we derive an explicit integral expression for the background scattering, which can be determined numerically from the static structure factors of the coexisting bulk phases as independent input. Concerning the interpretation of GIXRD data inferred from computer simulations, we extend the model to account also for the finite sizes of the bulk phases, which are unavoidable in simulations. The corresponding leading-order correction beyond the dominant contribution to the scattered intensity is revealed by asymptotic analysis, which is characterized by the competition between the linear system size and the x-ray penetration depth in the case of simulations. Specifically, we have calculated the expected GIXRD intensity for scattering at the planar liquid-vapor interface of Lennard-Jones fluids with truncated pair interactions via extensive, high-precision computer simulations. The reported data cover interfacial and bulk properties of fluid states along the whole liquid-vapor coexistence line. A sensitivity analysis shows that our findings are robust with respect to the detailed definition of the mean interface position. We conclude that previous claims of an enhanced surface tension at mesoscopic scales are amenable to unambiguous tests via scattering experiments.
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Affiliation(s)
- F Höfling
- Freie Universität Berlin, Fachbereich Mathematik und Informatik, Arnimallee 6, 14195 Berlin, Germany
- Zuse Institut Berlin, Takustr. 7, 14195 Berlin, Germany
| | - S Dietrich
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstraße 3, 70569 Stuttgart, Germany
- IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
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3
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Holland-Moritz D, Yang F, Hansen TC, Kargl F. Chemical short-range order in liquid Ni-Cu. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2023; 35:465403. [PMID: 37557891 DOI: 10.1088/1361-648x/aceee0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Accepted: 08/09/2023] [Indexed: 08/11/2023]
Abstract
Neutron diffraction in combination with isotopic substitution on the zero-scatterer62Ni4363Cu57shows indications for chemical short-range order in the stable liquid as evidenced by oscillations in the concentration-concentration structure factorSCC(q). This points towards a non-ideal solution behavior of Ni-Cu contrary to common believe but in agreement with measurements of free enthalpy of mixing. The temperature dependence ofSCCat small momentum transfer provides evidence of critical compositional fluctuations in Ni43Cu57melts.
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Affiliation(s)
- Dirk Holland-Moritz
- Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt, 51170 Köln, Germany
| | - Fan Yang
- Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt, 51170 Köln, Germany
| | | | - Florian Kargl
- Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt, 51170 Köln, Germany
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4
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Das K, Das SK. Hydrodynamic effects in kinetics of phase separation in binary fluids: Critical versus off-critical compositions. Phys Rev E 2023; 107:044116. [PMID: 37198773 DOI: 10.1103/physreve.107.044116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 03/28/2023] [Indexed: 05/19/2023]
Abstract
Via hydrodynamics-preserving molecular dynamics simulations we study growth phenomena in a phase-separating symmetric binary mixture model. We quench high-temperature homogeneous configurations to state points inside the miscibility gap, for various mixture compositions. For compositions at the symmetric or critical value we capture the rapid linear viscous hydrodynamic growth due to advective transport of material through tubelike interconnected domains. For state points very close to any of the branches of the coexistence curve, the growth in the system, following nucleation of disconnected droplets of the minority species, occurs via a coalescence mechanism. Using state-of-the-art techniques, we have identified that these droplets, between collisions, exhibit diffusive motion. The value of the exponent for the power-law growth, related to this diffusive coalescence mechanism, has been estimated. While the exponent nicely agrees with that for the growth via the well-known Lifshitz-Slyozov particle diffusion mechanism, the amplitude is stronger. For the intermediate compositions we observe initial rapid growth that matches the expectations for viscous or inertial hydrodynamic pictures. However, at later times these types of growth cross over to the exponent that is decided by the diffusive coalescence mechanism.
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Affiliation(s)
- Koyel Das
- Theoretical Sciences Unit and School of Advanced Materials, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India
| | - Subir K Das
- Theoretical Sciences Unit and School of Advanced Materials, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India
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5
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Longo TJ, Anisimov MA. Phase transitions affected by natural and forceful molecular interconversion. J Chem Phys 2022; 156:084502. [DOI: 10.1063/5.0081180] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
If a binary liquid mixture, composed of two alternative species with equal amounts, is quenched from a high temperature to a low temperature, below the critical point of demixing, then the mixture will phase separate through a process known as spinodal decomposition. However, if the two alternative species are allowed to interconvert, either naturally (e.g., the equilibrium interconversion of enantiomers) or forcefully (e.g., via an external source of energy or matter), then the process of phase separation may drastically change. In this case, depending on the nature of interconversion, two phenomena could be observed: either phase amplification, the growth of one phase at the expense of another stable phase, or microphase separation, the formation of nongrowing (steady-state) microphase domains. In this work, we phenomenologically generalize the Cahn–Hilliard theory of spinodal decomposition to include the molecular interconversion of species and describe the physical properties of systems undergoing either phase amplification or microphase separation. We apply the developed phenomenology to accurately describe the simulation results of three atomistic models that demonstrate phase amplification and/or microphase separation. We also discuss the application of our approach to phase transitions in polyamorphic liquids. Finally, we describe the effects of fluctuations of the order parameter in the critical region on phase amplification and microphase separation.
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Affiliation(s)
- Thomas J. Longo
- Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA
| | - Mikhail A. Anisimov
- Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA
- Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland 20742, USA
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6
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Shumovskyi NA, Longo TJ, Buldyrev SV, Anisimov MA. Phase amplification in spinodal decomposition of immiscible fluids with interconversion of species. Phys Rev E 2021; 103:L060101. [PMID: 34271768 DOI: 10.1103/physreve.103.l060101] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 05/20/2021] [Indexed: 11/07/2022]
Abstract
A fluid composed of two molecular species may undergo phase segregation via spinodal decomposition. However, if the two molecular species can interconvert, e.g., change their chirality, then a phenomenon of phase amplification, which has not been studied so far to our best knowledge, emerges. As a result, eventually, one phase will completely eliminate the other one. We model this phenomenon on an Ising system which relaxes to equilibrium through a hybrid of Kawasaki-diffusion and Glauber-interconversion dynamics. By introducing a probability of Glauber-interconversion dynamics, we show that the particle conservation law is broken, thus resulting in phase amplification. We characterize the speed of phase amplification through scaling laws based on the probability of Glauber dynamics, system size, and distance to the critical temperature of demixing.
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Affiliation(s)
| | - Thomas J Longo
- Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA
| | - Sergey V Buldyrev
- Department of Physics, Yeshiva University, New York, New York 10033, USA and Department of Physics, Boston University, Boston, Massachusetts 02215, USA
| | - Mikhail A Anisimov
- Department of Chemical and Biomolecular Engineering and Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA
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7
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Pathania Y, Chakraborty D, Höfling F. Continuous Demixing Transition of Binary Liquids: Finite‐Size Scaling from the Analysis of Sub‐Systems. ADVANCED THEORY AND SIMULATIONS 2021. [DOI: 10.1002/adts.202000235] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Yogyata Pathania
- Indian Institute of Science Education and Research Mohali Knowledge City, Sector 81, S. A. S. Nagar Manauli 140306 India
| | - Dipanjan Chakraborty
- Indian Institute of Science Education and Research Mohali Knowledge City, Sector 81, S. A. S. Nagar Manauli 140306 India
| | - Felix Höfling
- Freie Universität Berlin, Fachbereich Mathematik und Informatik Arnimallee 6 Berlin 14195 Germany
- Zuse Institute Berlin Takustr. 7 Berlin 14195 Germany
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Vadakkayil N, Das SK. Should a hotter paramagnet transform quicker to a ferromagnet? Monte Carlo simulation results for Ising model. Phys Chem Chem Phys 2021; 23:11186-11190. [PMID: 33949508 DOI: 10.1039/d1cp00879j] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
For quicker formation of ice, before inserting inside a refrigerator, heating up of a body of water can be beneficial. We report first observation of a counterpart of this intriguing fact, referred to as the Mpemba effect (ME), during ordering in ferromagnets. By performing Monte Carlo simulations of a generic model, we have obtained results on relaxation of systems that are quenched to sub-critical state points from various temperatures above the critical point. For a fixed final temperature, a system with higher starting temperature equilibrates faster than the one prepared at a lower temperature, implying the presence of ME. The observation is extremely counter-intuitive, particularly because of the fact that the model has no in-built frustration or metastability that typically is thought to provide ME. Via the calculations of nonequilibrium properties concerning structure and energy, we quantify the role of critical fluctuations behind this fundamental as well as technologically relevant observation.
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Affiliation(s)
- Nalina Vadakkayil
- Theoretical Sciences Unit and School of Advanced Materials, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064, India.
| | - Subir K Das
- Theoretical Sciences Unit and School of Advanced Materials, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064, India.
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9
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Casiulis M, Tarzia M, Cugliandolo LF, Dauchot O. Ferromagnetism-induced phase separation in a two-dimensional spin fluid. J Chem Phys 2019; 150:154501. [PMID: 31005076 DOI: 10.1063/1.5064590] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We study the liquid-gas phase separation observed in a system of repulsive particles dressed with ferromagnetically aligning spins, a so-called "spin fluid." Microcanonical ensemble numerical simulations of finite-size systems reveal that magnetization sets in and induces a liquid-gas phase separation between a disordered gas and a ferromagnetic dense phase at low enough energies and large enough densities. The dynamics after a quench into the coexistence region show that the order parameter associated with the liquid-vapor phase separation follows an algebraic law with an unusual exponent, as it is forced to synchronize with the growth of the magnetization: this suggests that for finite size systems the magnetization sets in along a Curie line, which is also the gas-side spinodal line, and that the coexistence region ends at a tricritical point. This picture is confirmed at the mean-field level with different approximation schemes, namely, a Bethe lattice resolution and a virial expansion complemented by the introduction of a self-consistent Weiss-like molecular field. However, a detailed finite-size scaling analysis shows that in two dimensions the ferromagnetic phase escapes the Berezinskii-Kosterlitz-Thouless scenario and that the long-range order is not destroyed by the unbinding of topological defects. The Curie line thus becomes a magnetic crossover in the thermodynamic limit. Finally, the effects of the magnetic interaction range and those of the interaction softness are characterized within a mean-field semianalytical low-density approach.
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Affiliation(s)
- Mathias Casiulis
- Sorbonne Université, Laboratoire de Physique Théorique de la Matière Condensée, CNRS UMR 7600, 4 Place Jussieu, F-75005 Paris, France
| | - Marco Tarzia
- Sorbonne Université, Laboratoire de Physique Théorique de la Matière Condensée, CNRS UMR 7600, 4 Place Jussieu, F-75005 Paris, France
| | - Leticia F Cugliandolo
- Sorbonne Université, Laboratoire de Physique Théorique et Hautes Énergies, CNRS UMR 7589, 4 Place Jussieu, F-75005 Paris, France
| | - Olivier Dauchot
- PSL Research University, Laboratoire Gulliver, CNRS UMR 7083, ESPCI Paris, 10 rue Vauquelin, 75005 Paris, France
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10
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11
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Thorneywork AL, Schnyder SK, Aarts DGAL, Horbach J, Roth R, Dullens RPA. Structure factors in a two-dimensional binary colloidal hard sphere system. Mol Phys 2018. [DOI: 10.1080/00268976.2018.1492745] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Alice L. Thorneywork
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford, UK
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Simon K. Schnyder
- Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto, Japan
| | - Dirk G. A. L. Aarts
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford, UK
| | - Jürgen Horbach
- Institut für Theoretische Physik II, Heinrich-Heine Universität Düsseldorf, Düsseldorf, Germany
| | - Roland Roth
- Institut für Theoretische Physik, Universität Tübingen, Tübingen, Germany
| | - Roel P. A. Dullens
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford, UK
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12
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Affiliation(s)
- Jingxiang Guo
- Department of Chemical and Biomolecular Engineering, University of Houston , Houston, TX, USA
| | - Rakesh S. Singh
- Department of Chemistry, Johns Hopkins University , Baltimore, MD, USA
| | - Jeremy C. Palmer
- Department of Chemical and Biomolecular Engineering, University of Houston , Houston, TX, USA
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13
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Guo J, Palmer JC. Fluctuations near the liquid–liquid transition in a model of silica. Phys Chem Chem Phys 2018; 20:25195-25202. [DOI: 10.1039/c8cp04237c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Molecular dynamics simulations reveal anomalous small-angle scattering and liquid–liquid phase separation in an ionic model of silica.
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Affiliation(s)
- Jingxiang Guo
- Department of Chemical and Biomolecular Engineering
- University of Houston
- Houston
- USA
| | - Jeremy C. Palmer
- Department of Chemical and Biomolecular Engineering
- University of Houston
- Houston
- USA
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14
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Gross M, Gambassi A, Dietrich S. Statistical field theory with constraints: Application to critical Casimir forces in the canonical ensemble. Phys Rev E 2017; 96:022135. [PMID: 28950535 DOI: 10.1103/physreve.96.022135] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Indexed: 06/07/2023]
Abstract
The effect of imposing a constraint on a fluctuating scalar order parameter field in a system of finite volume is studied within statistical field theory. The canonical ensemble, corresponding to a fixed total integrated order parameter (e.g., the total number of particles), is obtained as a special case of the theory. A perturbative expansion is developed which allows one to systematically determine the constraint-induced finite-volume corrections to the free energy and to correlation functions. In particular, we focus on the Landau-Ginzburg model in a film geometry (i.e., in a rectangular parallelepiped with a small aspect ratio) with periodic, Dirichlet, or Neumann boundary conditions in the transverse direction and periodic boundary conditions in the remaining, lateral directions. Within the expansion in terms of ε=4-d, where d is the spatial dimension of the bulk, the finite-size contribution to the free energy of the confined system and the associated critical Casimir force are calculated to leading order in ε and are compared to the corresponding expressions for an unconstrained (grand canonical) system. The constraint restricts the fluctuations within the system and it accordingly modifies the residual finite-size free energy. The resulting critical Casimir force is shown to depend on whether it is defined by assuming a fixed transverse area or a fixed total volume. In the former case, the constraint is typically found to significantly enhance the attractive character of the force as compared to the grand canonical case. In contrast to the grand canonical Casimir force, which, for supercritical temperatures, vanishes in the limit of thick films, in the canonical case with fixed transverse area the critical Casimir force attains for thick films a negative value for all boundary conditions studied here. Typically, the dependence of the critical Casimir force both on the temperaturelike and on the fieldlike scaling variables is different in the two ensembles.
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Affiliation(s)
- Markus Gross
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstraße 3, 70569 Stuttgart, Germany
- IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
| | - Andrea Gambassi
- SISSA-International School for Advanced Studies and INFN, via Bonomea 265, 34136 Trieste, Italy
| | - S Dietrich
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstraße 3, 70569 Stuttgart, Germany
- IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
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15
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16
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Midya J, Das SK. Finite-size scaling study of dynamic critical phenomena in a vapor-liquid transition. J Chem Phys 2017; 146:044503. [PMID: 28147549 DOI: 10.1063/1.4974506] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Via a combination of molecular dynamics (MD) simulations and finite-size scaling (FSS) analysis, we study dynamic critical phenomena for the vapor-liquid transition in a three dimensional Lennard-Jones system. The phase behavior of the model has been obtained via the Monte Carlo simulations. The transport properties, viz., the bulk viscosity and the thermal conductivity, are calculated via the Green-Kubo relations, by taking inputs from the MD simulations in the microcanonical ensemble. The critical singularities of these quantities are estimated via the FSS method. The results thus obtained are in nice agreement with the predictions of the dynamic renormalization group and mode-coupling theories.
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Affiliation(s)
- Jiarul Midya
- Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064, India
| | - Subir K Das
- Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064, India
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17
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Patrykiejew A. Effects of geometrical and energetic nonadditivity on the phase behavior of two-component symmetric mixtures. Phys Rev E 2017; 95:012145. [PMID: 28208461 DOI: 10.1103/physreve.95.012145] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Indexed: 06/06/2023]
Abstract
Using Monte Carlo simulation methods in the grand-canonical ensemble, we have studied the phase behavior of three-dimensional symmetric binary mixtures of Lennard-Jones particles. We have also elucidated the effects of geometric and energetic nonadditivity on the phase behavior. Phase diagrams for several systems have been evaluated. We have demonstrated that in completely miscible mixtures the geometrical nonadditivity (negative as well as positive) stabilizes a liquid phase leading to a gradual increase of the critical temperature. The mechanism leading to such behavior is different when the system shows negative and positive geometrical nonadditivity. In the case of systems with negative energetic nonadditivity, which may exhibit demixing transition in the liquid phase, their phase behavior is also strongly affected by the geometric non-additivity. The systems with negative geometric nonadditivity have been demonstrated to show reentrant miscibility, while those with positive geometric nonadditivity show enhanced tendency toward mixing at sufficiently high temperatures. We have evaluated phase diagrams for several systems.
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Affiliation(s)
- A Patrykiejew
- Department for the Modelling of Physico-Chemical Processes, Faculty of Chemistry, MCS University, 20031 Lublin, Poland
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18
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Toda M, Kajimoto S, Toyouchi S, Kawakatsu T, Akama Y, Kotani M, Fukumura H. Phase behavior of a binary fluid mixture of quadrupolar molecules. Phys Rev E 2016; 94:052601. [PMID: 27967026 DOI: 10.1103/physreve.94.052601] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Indexed: 06/06/2023]
Abstract
We propose a model molecule to investigate microscopic properties of a binary mixture with a closed-loop coexistence region. The molecule is comprised of a Lennard-Jones particle and a uniaxial quadrupole. Gibbs ensemble Monte Carlo simulations demonstrate that the high-density binary fluid of the molecules with the quadrupoles of the same magnitude but of the opposite signs can show closed-loop immiscibility. We find that an increase in the magnitude of the quadrupoles causes a shrinkage of the coexistence region. Molecular dynamics simulations also reveal that aggregates with two types of molecules arranged alternatively are formed in the stable one-phase region both above and below the coexistence region. String structures are dominant below the lower critical solution temperature, while branched aggregates are observed above the upper critical solution temperature. We conclude that the anisotropic interaction between the quadrupoles of the opposite signs plays a crucial role in controlling these properties of the phase behavior.
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Affiliation(s)
- Masatoshi Toda
- Department of Chemistry, Tohoku University, Sendai, 980-8578, Japan
| | - Shinji Kajimoto
- Department of Chemistry, Tohoku University, Sendai, 980-8578, Japan
| | - Shuichi Toyouchi
- Department of Chemistry, Tohoku University, Sendai, 980-8578, Japan
| | | | - Yohji Akama
- Mathematical Institute, Tohoku University, Sendai, 980-8578, Japan
| | - Motoko Kotani
- Mathematical Institute, Tohoku University, Sendai, 980-8578, Japan
- WPI-AIMR, Tohoku University, Sendai, 980-8577, Japan
| | - Hiroshi Fukumura
- Department of Chemistry, Tohoku University, Sendai, 980-8578, Japan
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19
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Roy S, Dietrich S, Höfling F. Structure and dynamics of binary liquid mixtures near their continuous demixing transitions. J Chem Phys 2016; 145:134505. [DOI: 10.1063/1.4963771] [Citation(s) in RCA: 22] [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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20
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Puosi F, Cardozo DL, Ciliberto S, Holdsworth PCW. Direct calculation of the critical Casimir force in a binary fluid. Phys Rev E 2016; 94:040102. [PMID: 27841545 DOI: 10.1103/physreve.94.040102] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Indexed: 06/06/2023]
Abstract
We show that critical Casimir effects can be accessed through direct simulation of a model binary fluid passing through the demixing transition. We work in the semi-grand-canonical ensemble, in slab geometry, in which the Casimir force appears as the excess of the generalized pressure, P_{⊥}-nμ. The excesses of the perpendicular pressure, P_{⊥}, and of nμ, are individually of much larger amplitude. A critical pressure anisotropy is observed between forces parallel and perpendicular to the confinement direction, which collapses onto a universal scaling function closely related to that of the critical Casimir force.
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Affiliation(s)
- Francesco Puosi
- Université de Lyon, Laboratoire de Physique, École normale supérieure de Lyon, CNRS, UMR5672, 46 Allée d'Italie, 69364 Lyon, France
| | - David Lopes Cardozo
- Université de Lyon, Laboratoire de Physique, École normale supérieure de Lyon, CNRS, UMR5672, 46 Allée d'Italie, 69364 Lyon, France
| | - Sergio Ciliberto
- Université de Lyon, Laboratoire de Physique, École normale supérieure de Lyon, CNRS, UMR5672, 46 Allée d'Italie, 69364 Lyon, France
| | - Peter C W Holdsworth
- Université de Lyon, Laboratoire de Physique, École normale supérieure de Lyon, CNRS, UMR5672, 46 Allée d'Italie, 69364 Lyon, France
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21
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Gross M, Vasilyev O, Gambassi A, Dietrich S. Critical adsorption and critical Casimir forces in the canonical ensemble. Phys Rev E 2016; 94:022103. [PMID: 27627242 DOI: 10.1103/physreve.94.022103] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Indexed: 06/06/2023]
Abstract
Critical properties of a liquid film between two planar walls are investigated in the canonical ensemble, within which the total number of fluid particles, rather than their chemical potential, is kept constant. The effect of this constraint is analyzed within mean-field theory (MFT) based on a Ginzburg-Landau free-energy functional as well as via Monte Carlo simulations of the three-dimensional Ising model with fixed total magnetization. Within MFT and for finite adsorption strengths at the walls, the thermodynamic properties of the film in the canonical ensemble can be mapped exactly onto a grand canonical ensemble in which the corresponding chemical potential plays the role of the Lagrange multiplier associated with the constraint. However, due to a nonintegrable divergence of the mean-field order parameter profile near a wall, the limit of infinitely strong adsorption turns out to be not well-defined within MFT, because it would necessarily violate the constraint. The critical Casimir force (CCF) acting on the two planar walls of the film is generally found to behave differently in the canonical and grand canonical ensembles. For instance, the canonical CCF in the presence of equal preferential adsorption at the two walls is found to have the opposite sign and a slower decay behavior as a function of the film thickness compared to its grand canonical counterpart. We derive the stress tensor in the canonical ensemble and find that it has the same expression as in the grand canonical case, but with the chemical potential playing the role of the Lagrange multiplier associated with the constraint. The different behavior of the CCF in the two ensembles is rationalized within MFT by showing that, for a prescribed value of the thermodynamic control parameter of the film, i.e., density or chemical potential, the film pressures are identical in the two ensembles, while the corresponding bulk pressures are not.
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Affiliation(s)
- Markus Gross
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstraße 3, 70569 Stuttgart, Germany
- IV Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
| | - Oleg Vasilyev
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstraße 3, 70569 Stuttgart, Germany
- IV Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
| | - Andrea Gambassi
- SISSA-International School for Advanced Studies and INFN, via Bonomea 265, 34136 Trieste, Italy
| | - S Dietrich
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstraße 3, 70569 Stuttgart, Germany
- IV Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
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Cardozo DL, Holdsworth PCW. Finite-size scaling of the magnetization probability density for the critical Ising model in slab geometry. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:166007. [PMID: 27022780 DOI: 10.1088/0953-8984/28/16/166007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The magnetization probability density in d = 2 and 3 dimensional Ising models in slab geometry of volume [Formula: see text] is computed through Monte-Carlo simulation at the critical temperature and zero magnetic field. The finite-size scaling of this distribution and its dependence on the system aspect-ratio [Formula: see text]and boundary conditions are discussed. In the limiting case [Formula: see text] of a macroscopically large slab ([Formula: see text]) the distribution is found to scale as a Gaussian function for all tested system sizes and boundary conditions.
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Affiliation(s)
- David Lopes Cardozo
- Laboratoire de Physique, École Normale Supérieure de Lyon, Université de Lyon, UMR CNRS 5672, 46 Allée d'Italie, 69364 Lyon Cedex 07, France
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Roy S, Das SK. Study of critical dynamics in fluids via molecular dynamics in canonical ensemble. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2015; 38:132. [PMID: 26687057 DOI: 10.1140/epje/i2015-15132-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Accepted: 11/30/2015] [Indexed: 06/05/2023]
Abstract
With the objective of understanding the usefulness of thermostats in the study of dynamic critical phenomena in fluids, we present results for transport properties in a binary Lennard-Jones fluid that exhibits liquid-liquid phase transition. Various collective transport properties, calculated from the molecular dynamics (MD) simulations in canonical ensemble, with different thermostats, are compared with those obtained from MD simulations in microcanonical ensemble. It is observed that the Nosé-Hoover and dissipative particle dynamics thermostats are useful for the calculations of mutual diffusivity and shear viscosity. The Nosé-Hoover thermostat, however, as opposed to the latter, appears inadequate for the study of bulk viscosity.
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Affiliation(s)
- Sutapa Roy
- Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O, 560064, Bangalore, India
| | - Subir K Das
- Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O, 560064, Bangalore, India.
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24
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Krishnan R, Puri S. Molecular dynamics study of phase separation in fluids with chemical reactions. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:052316. [PMID: 26651704 DOI: 10.1103/physreve.92.052316] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Indexed: 06/05/2023]
Abstract
We present results from the first d=3 molecular dynamics (MD) study of phase-separating fluid mixtures (AB) with simple chemical reactions (A⇌B). We focus on the case where the rates of forward and backward reactions are equal. The chemical reactions compete with segregation, and the coarsening system settles into a steady-state mesoscale morphology. However, hydrodynamic effects destroy the lamellar morphology which characterizes the diffusive case. This has important consequences for the phase-separating structure, which we study in detail. In particular, the equilibrium length scale (ℓ(eq)) in the steady state suggests a power-law dependence on the reaction rate ε:ℓ(eq)∼ε(-θ) with θ≃1.0.
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Affiliation(s)
- Raishma Krishnan
- School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067, India
| | - Sanjay Puri
- School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067, India
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25
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Roy S, Das SK. Finite-size scaling study of shear viscosity anomaly at liquid-liquid criticality. J Chem Phys 2015; 141:234502. [PMID: 25527943 DOI: 10.1063/1.4903810] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We study the equilibrium dynamics of a symmetrical binary Lennard-Jones fluid mixture near its consolute criticality. Molecular dynamics simulation results for the shear viscosity, η, from a microcanonical ensemble are compared with those from a canonical ensemble with various thermostats. It is observed that the Nosé-Hoover thermostat is a good candidate for this purpose, and is therefore adopted for the quantification of the critical singularity of η, to avoid the temperature fluctuations (or even drifts) that are often encountered in microcanonical simulations. Via a finite-size scaling analysis of our simulation data we have been able to confirm that the shear viscosity exhibits a weak critical singularity in agreement with the theoretical predictions.
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Affiliation(s)
- Sutapa Roy
- Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064, India
| | - Subir K Das
- Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064, India
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26
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Das SK. Atomistic simulations of liquid–liquid coexistence in confinement: comparison of thermodynamics and kinetics with bulk. MOLECULAR SIMULATION 2015. [DOI: 10.1080/08927022.2014.998214] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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27
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Ahmad S, Puri S, Das SK. Phase separation of fluids in porous media: a molecular dynamics study. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 90:040302. [PMID: 25375423 DOI: 10.1103/physreve.90.040302] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Indexed: 06/04/2023]
Abstract
We present comprehensive molecular dynamics results for phase-separation kinetics of fluids in a porous medium. This system is modeled by a symmetric Lennard-Jones fluid mixture with a quenched random field. The presence of disorder slows down domain growth from power-law to a logarithmic form. It also modifies the correlation functions and structure factors which characterize the morphology. In particular, the structure-factor tail shows a non-Porod behavior, which is the consequence of scattering from rough interfaces.
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Affiliation(s)
- Shaista Ahmad
- School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067, India
| | - Sanjay Puri
- School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067, India
| | - Subir K Das
- Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064, India
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28
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Roy S, Das SK. Simulation of transport around the coexistence region of a binary fluid. J Chem Phys 2014; 139:064505. [PMID: 23947869 DOI: 10.1063/1.4817777] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We use Monte Carlo and molecular dynamics simulations to study phase behavior and transport properties in a symmetric binary fluid where particles interact via Lennard-Jones potential. Our results for the critical behavior of collective transport properties, with particular emphasis on bulk viscosity, is understood via appropriate application of finite-size scaling technique. It appears that the critical enhancements in these quantities are visible far above the critical point. This result is consistent with an earlier report from computer simulations where, however, the authors do not quantify the critical singularity.
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Affiliation(s)
- Sutapa Roy
- Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064, India
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Singh A, Puri S, Dasgupta C. Kinetics of phase separation in polymer mixtures: A molecular dynamics study. J Chem Phys 2014; 140:244906. [DOI: 10.1063/1.4884824] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Awaneesh Singh
- Department of Physics, Indian Institute of Science, Bangalore – 560012, India
- School of Physical Sciences, Jawaharlal Nehru University, New Delhi – 110067, India
| | - Sanjay Puri
- School of Physical Sciences, Jawaharlal Nehru University, New Delhi – 110067, India
| | - Chandan Dasgupta
- Department of Physics, Indian Institute of Science, Bangalore – 560012, India
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30
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Binder K. Simulations of Interfacial Phenomena in Soft Condensed Matter and Nanoscience. ACTA ACUST UNITED AC 2014. [DOI: 10.1088/1742-6596/510/1/012002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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31
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Materniak S, Patrykiejew A. Symmetrical mixtures in external fields. J Chem Phys 2013; 139:014705. [DOI: 10.1063/1.4812370] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
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32
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Vasilyev OA, Klumov BA, Tkachenko AV. Precursors of order in aggregates of patchy particles. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 88:012302. [PMID: 23944458 DOI: 10.1103/physreve.88.012302] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Indexed: 06/02/2023]
Abstract
We study computationally the local structure of aggregated systems of patchy particles. By calculating the probability distribution functions of various rotational invariants we can identify the precursors of orientation order in amorphous phase. Surprisingly, the strongest signature of local order is observed for four-patch particles with tetrahedral symmetry, not for six-patch particles with the cubic one. This trend is exactly opposite to their known ability to crystallize. We relate this anomaly to the observation that a generic aggregate of patchy systems has a coordination number close to 4. Our results also suggest a significant correlation between rotational order in the studied liquids with the corresponding crystalline phases, making this approach potentially useful for a broader range of patchy systems.
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Affiliation(s)
- Oleg A Vasilyev
- Max-Planck-Institut für Intelligente Systeme, Stuttgart, Germany
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33
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Materniak S, Patrykiejew A, Rżysko W. Reentrant miscibility in two-dimensional symmetrical mixtures. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 87:062306. [PMID: 23848674 DOI: 10.1103/physreve.87.062306] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Indexed: 06/02/2023]
Abstract
The Monte Carlo simulation method in the grand canonical ensemble is used to study the phase behavior of two-dimensional symmetrical binary mixtures of Lennard-Jones particles with negative nonadditivity and the weaker interaction between the pairs of unlike than between the pairs of like particles. We have determined the evolution of the phase diagram topology when the parameters describing the interaction between unlike particles vary. It has been found that such systems may exhibit reentrant miscibility in the liquid and the solid phases.
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Affiliation(s)
- S Materniak
- Department for the Modelling of Physico-Chemical Processes, Faculty of Chemistry, MCS University, 20031 Lublin, Poland
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34
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Rudavets MG. Effective dipole-dipole interactions in critical nanofluids. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 230:10-18. [PMID: 23416706 DOI: 10.1016/j.jmr.2013.01.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Revised: 12/21/2012] [Accepted: 01/07/2013] [Indexed: 06/01/2023]
Abstract
It is long known that the effective dipole-dipole coupling is averaged to zero when the spin carrying atoms are involved in a fast random movement in an unconfined fluid. The presented theory shows that if (i) the fluid is confined in long closed nanotubes, (ii) the fluid is in the vicinity of the second order phase transition, and (iii) the mobility of the spin carrying atoms of the fluid is high then the effective dipole-dipole coupling of the fluid is characterized by a finite global value that is independent of the spacing between all the atoms and independent of the length of the nanotubes. We report how the two regimes of the strong and weak effective dipole-dipole couplings in the vicinity and far from the critical point (CP), respectively, can be discriminated in the NMR experiments. Strong enhancements of the signals in the free induction decay, the line shape and the superradiation that result from the abnormally large effective dipole-dipole coupling in the vicinity of the CP are predicted.
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Affiliation(s)
- M G Rudavets
- Institute of Problems of Chemical Physics, RAS, Chernogolovka, Moscow Region 142432, Russia.
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35
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Höfling F, Franosch T. Anomalous transport in the crowded world of biological cells. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2013; 76:046602. [PMID: 23481518 DOI: 10.1088/0034-4885/76/4/046602] [Citation(s) in RCA: 584] [Impact Index Per Article: 53.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
A ubiquitous observation in cell biology is that the diffusive motion of macromolecules and organelles is anomalous, and a description simply based on the conventional diffusion equation with diffusion constants measured in dilute solution fails. This is commonly attributed to macromolecular crowding in the interior of cells and in cellular membranes, summarizing their densely packed and heterogeneous structures. The most familiar phenomenon is a sublinear, power-law increase of the mean-square displacement (MSD) as a function of the lag time, but there are other manifestations like strongly reduced and time-dependent diffusion coefficients, persistent correlations in time, non-Gaussian distributions of spatial displacements, heterogeneous diffusion and a fraction of immobile particles. After a general introduction to the statistical description of slow, anomalous transport, we summarize some widely used theoretical models: Gaussian models like fractional Brownian motion and Langevin equations for visco-elastic media, the continuous-time random walk model, and the Lorentz model describing obstructed transport in a heterogeneous environment. Particular emphasis is put on the spatio-temporal properties of the transport in terms of two-point correlation functions, dynamic scaling behaviour, and how the models are distinguished by their propagators even if the MSDs are identical. Then, we review the theory underlying commonly applied experimental techniques in the presence of anomalous transport like single-particle tracking, fluorescence correlation spectroscopy (FCS) and fluorescence recovery after photobleaching (FRAP). We report on the large body of recent experimental evidence for anomalous transport in crowded biological media: in cyto- and nucleoplasm as well as in cellular membranes, complemented by in vitro experiments where a variety of model systems mimic physiological crowding conditions. Finally, computer simulations are discussed which play an important role in testing the theoretical models and corroborating the experimental findings. The review is completed by a synthesis of the theoretical and experimental progress identifying open questions for future investigation.
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Affiliation(s)
- Felix Höfling
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstraße 3, 70569 Stuttgart, and Institut für Theoretische Physik IV, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
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36
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Mutoru JW, Smith W, O’Hern CS, Firoozabadi A. Molecular dynamics simulations of diffusion and clustering along critical isotherms of medium-chain n-alkanes. J Chem Phys 2013; 138:024317. [DOI: 10.1063/1.4773282] [Citation(s) in RCA: 9] [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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37
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Fang T, Wang L, Peng CX, Qi Y. Liquid immiscibility in an Fe-Cu alloy by molecular dynamics simulation. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:505103. [PMID: 23164973 DOI: 10.1088/0953-8984/24/50/505103] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Liquid-liquid phase segregation in an Fe-Cu melt is investigated by molecular dynamics (MD) simulation based upon a newly developed embedded atom method due to Bonny. The partial pair correlation functions (PPCF) of liquid Fe(50)Cu(50) at a temperature of 1873 K show stronger interaction of homogeneous atom pairs. The coordination number (CN) of Cu-Cu and Fe-Fe in Fe(50)Cu(50) melt is about 11, much higher than that of Fe-Cu. Liquid-liquid phase segregation has also been observed clearly by the atom snapshot method. The calculated enthalpy of mixing is positive in the whole concentration range and the Bhatia-Thornton (BT) structure factor S(CC)(q) increases sharply at lower q, which are all typical features of dense fluid that exhibits a phase segregation tendency. Our present work provides an understanding of atomic-scale phase segregation in liquid Fe-Cu alloy.
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Affiliation(s)
- T Fang
- School of Mechanical and Electrical and Information Engineering, Shandong University at Weihai, Weihai 264209, People's Republic of China
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Gross M, Varnik F. Critical dynamics of an isothermal compressible nonideal fluid. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 86:061119. [PMID: 23367905 DOI: 10.1103/physreve.86.061119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Revised: 08/23/2012] [Indexed: 06/01/2023]
Abstract
A pure fluid at its critical point shows a dramatic slow-down in its dynamics, due to a divergence of the order-parameter susceptibility and the coefficient of heat transport. Under isothermal conditions, however, sound waves provide the only possible relaxation mechanism for order-parameter fluctuations. Here we study the critical dynamics of an isothermal, compressible nonideal fluid via scaling arguments and computer simulations of the corresponding fluctuating hydrodynamics equations. We show that, below a critical dimension of 4, the order-parameter dynamics of an isothermal fluid effectively reduces to "model A," characterized by overdamped sound waves and a divergent bulk viscosity. In contrast, the shear viscosity remains finite above two dimensions. Possible applications of the model are discussed.
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Affiliation(s)
- Markus Gross
- Interdisciplinary Centre for Advanced Materials Simulation, Ruhr-Universität Bochum, Universitätsstr 90a, 44789 Bochum, Germany.
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39
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Ahmad S, Corberi F, Das SK, Lippiello E, Puri S, Zannetti M. Aging and crossovers in phase-separating fluid mixtures. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 86:061129. [PMID: 23367915 DOI: 10.1103/physreve.86.061129] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2012] [Revised: 11/22/2012] [Indexed: 06/01/2023]
Abstract
We use state-of-the-art molecular dynamics simulations to study hydrodynamic effects on aging during kinetics of phase separation in a fluid mixture. The domain growth law shows a crossover from a diffusive regime to a viscous hydrodynamic regime. There is a corresponding crossover in the autocorrelation function from a power-law behavior to an exponential decay. While the former is consistent with theories for diffusive domain growth, the latter results as a consequence of faster advective transport in fluids for which an analytical justification has been provided.
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Affiliation(s)
- Shaista Ahmad
- Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur PO, Bangalore 560064, India
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40
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Gross M, Varnik F. Simulation of static critical phenomena in nonideal fluids with the lattice Boltzmann method. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 85:056707. [PMID: 23004903 DOI: 10.1103/physreve.85.056707] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Indexed: 06/01/2023]
Abstract
A fluctuating nonideal fluid at its critical point is simulated with the lattice Boltzmann method. It is demonstrated that the method, employing a Ginzburg-Landau free energy functional, correctly reproduces the static critical behavior associated with the Ising universality class. A finite-size scaling analysis is applied to determine the critical exponents related to the order parameter, compressibility and specific heat. A particular focus is put on finite-size effects and issues related to the global conservation of the order parameter.
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Affiliation(s)
- M Gross
- Interdisciplinary Centre for Advanced Materials Simulation, Ruhr-Universität Bochum, Germany.
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41
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Jaiswal PK, Puri S, Das SK. Surface-directed spinodal decomposition: a molecular dynamics study. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 85:051137. [PMID: 23004733 DOI: 10.1103/physreve.85.051137] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Indexed: 06/01/2023]
Abstract
We use molecular dynamics simulations to study surface-directed spinodal decomposition in unstable binary AB fluid mixtures at wetting surfaces. The thickness of the wetting layer R1 grows with time t as a power law (R1∼tθ). We find that hydrodynamic effects result in a crossover of the growth exponent from θ≃1/3 to 1. We also present results for the layerwise correlation functions and domain length scales.
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Affiliation(s)
- Prabhat K Jaiswal
- School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110 067, India
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42
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Ahmad S, Das SK, Puri S. Crossover in growth laws for phase-separating binary fluids: molecular dynamics simulations. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 85:031140. [PMID: 22587071 DOI: 10.1103/physreve.85.031140] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Indexed: 05/31/2023]
Abstract
Pattern and dynamics during phase separation in a symmetrical binary (A+B) Lennard-Jones fluid are studied via molecular dynamics simulations after quenching homogeneously mixed critical (50:50) systems to temperatures below the critical one. The morphology of the domains, rich in A or B particles, is observed to be bicontinuous. The early-time growth of the average domain size is found to be consistent with the Lifshitz-Slyozov law for diffusive domain coarsening. After a characteristic time, dependent on the temperature, we find a clear crossover to an extended viscous hydrodynamic regime where the domains grow linearly with time. Pattern formation in the present system is compared with that in solid binary mixtures, as a function of temperature. Important results for the finite-size and temperature effects on the small-wave-vector behavior of the scattering function are also presented.
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Affiliation(s)
- Shaista Ahmad
- Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur Post Office, Bangalore, India
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43
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Das SK, Binder K. Universal critical behavior of curvature-dependent interfacial tension. PHYSICAL REVIEW LETTERS 2011; 107:235702. [PMID: 22182102 DOI: 10.1103/physrevlett.107.235702] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Indexed: 05/31/2023]
Abstract
From the analysis of Monte Carlo simulations of a binary Lennard-Jones mixture in the coexistence region, we provide evidence that the curvature dependence of the interfacial tension can be described by a simple theoretical function σ(R)ξ(2)=C(1)/[1+C(2)(ξ/R)(2)], where ξ is the correlation length and R is the droplet radius. The universal constants C(1) and C(2) are estimated. In the model, a Tolman length is strictly absent, but, since its critical behavior is believed to be much weaker than ξ, we argue that it only provides a correction to scaling and does not affect the leading critical behavior, which should be described by the above function for any system in the Ising universality class. The large value of C(2)≃32 implies that conventional nucleation theory becomes inaccurate even for a significantly large droplet radius.
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Affiliation(s)
- Subir K Das
- Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064, India
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Das SK, Binder K. Thermodynamic properties of a symmetrical binary mixture in the coexistence region. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 84:061607. [PMID: 22304102 DOI: 10.1103/physreve.84.061607] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Indexed: 05/31/2023]
Abstract
A three-dimensional symmetric binary fluid is studied, as a function of temperature, in the two-phase (liquid-liquid) coexistence region via Monte Carlo simulations. Particular focus has been in the understanding of curvature-dependent interfacial tension, which is observed to vary as σ(R) = σ(∞)/[1+2(ℓ/R)(2)], implying that a Tolman length is zero in the limit R → ∞. The length ℓ is found to have a critical divergence the same as the correlation length, but its amplitude is significantly larger (ℓ ~/= 4ξ). Our findings hence imply that the barrier against homogeneous nucleation is significantly reduced (in comparison with the classical nucleation theory) in the critical region. We also report results for the critical behavior of the flat interfacial tension σ(∞) and the concentration susceptibility, as well as the amplitude ratios involving these thermodynamic quantities. Noting that the interatomic potential in our model is described by the Lennard-Jones form that decays faster that 1/r(3), all of our results for critical phenomena are expectedly consistent with the Ising universality class of three spatial dimensions.
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Affiliation(s)
- Subir K Das
- Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur PO, Bangalore 560064, India
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Materniak S, Patrykiejew A, Sokołowski S. The phase behavior of two-dimensional symmetrical mixtures in a weak external field of square symmetry. J Chem Phys 2011; 134:214705. [DOI: 10.1063/1.3583984] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
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Das SK, Binder K. Simulation of binary fluids exposed to selectively adsorbing walls: a method to estimate contact angles and line tensions. Mol Phys 2011. [DOI: 10.1080/00268976.2010.541890] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Amore S, Horbach J, Egry I. Is there a relation between excess volume and miscibility in binary liquid mixtures? J Chem Phys 2011; 134:044515. [DOI: 10.1063/1.3528217] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Freyland W. Liquid Metals, Molten Salts, and Ionic Liquids: Some Basic Properties. SPRINGER SERIES IN SOLID-STATE SCIENCES 2011. [DOI: 10.1007/978-3-642-17779-8_2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
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Materniak S, Patrykiejew A, Sokołowski S. The phase behavior of two-dimensional symmetrical mixtures. J Chem Phys 2010; 133:244501. [PMID: 21197996 DOI: 10.1063/1.3511711] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Using Monte Carlo simulation methods in the grand canonical and semigrand canonical ensembles, we study the phase behavior of two-dimensional symmetrical binary mixtures of Lennard-Jones particles. We discuss the interplay between the demixing transition in a liquid and the freezing in detail. Phase diagrams for several systems characterized by different parameters describing interactions in the system are presented. It is explicitly demonstrated that different scenarios involving demixing and freezing transitions, described in our earlier paper [A. Patrykiejew and S. Sokołowski, Phys. Rev. E, 81, 012501 (2010)], are possible. In one class of systems, the λ-line representing a continuous demixing transition in a liquid phase starts at the liquid side of either the vapor-liquid or liquid-solid coexistence. The second class involves the systems in which the λ-line begins at the liquid side of the vapor-liquid coexistence, in the lower critical end point, and then terminates at the liquid side of the liquid-solid coexistence, in the upper critical end point. It is also shown that in such systems the solid phase may undergo a demixing transition at the temperature above the upper critical end point.
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Affiliation(s)
- S Materniak
- Department for the Modelling of Physico-Chemical Processes, Faculty of Chemistry, MCS University, 20031 Lublin, Poland
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Block BJ, Das SK, Oettel M, Virnau P, Binder K. Curvature dependence of surface free energy of liquid drops and bubbles: A simulation study. J Chem Phys 2010; 133:154702. [DOI: 10.1063/1.3493464] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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