1
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Singh A, Singh Y. Structure ordering and glass transition in size-asymmetric ternary mixtures of hard spheres: Variation from fragile to strong glasses. Phys Rev E 2023; 107:014119. [PMID: 36797956 DOI: 10.1103/physreve.107.014119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 12/21/2022] [Indexed: 01/15/2023]
Abstract
We investigate the structure and activated dynamics of a binary mixture of colloidal particles dispersed in a solvent of much smaller-sized particles. The solvent degrees of freedom are traced out from the grand partition function of the colloid-solvent mixture which reduces the system from ternary to effective binary mixture of colloidal particles. In the effective binary mixture colloidal particles interact via effective potential that consists of bare potential plus the solvent-induced interaction. Expressions for the effective potentials and pair correlation functions are derived. We used the result of pair correlation functions to determine the number of particles in a cooperatively reorganizing cluster (CRC) in which localized particles form "long-lived" nonchemical bonds with the central particle. For an event of relaxation to take place these bonds have to reorganize irreversibly, the energy involved in the processes is the effective activation energy of relaxation. Results are reported for hard sphere colloidal particles dispersed in a solvent of hard sphere particles. Our results show that the concentration of solvent can be used as a control parameter to fine-tune the microscopic structural ordering and the size of CRC that governs the glassy dynamics. We show that a small variation in the concentration of solvent creates a bigger change in the kinetic fragility which highlights a wide variation in behavior, ranging from fragile to strong glasses. We conclude that the CRC which is determined from the static pair correlation function and the fluctuations embedded in the system is probably the sole player in the physics of glass transition.
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Affiliation(s)
- Ankit Singh
- Department of Physics, Banaras Hindu University, Varanasi 221 005, India
| | - Yashwant Singh
- Department of Physics, Banaras Hindu University, Varanasi 221 005, India
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2
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Diaz Maier J, Wagner J. Viscoelastic properties of pNIPAM-hydrogels: A mode-coupling theory study. J Chem Phys 2022; 157:114901. [PMID: 36137810 DOI: 10.1063/5.0097841] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We investigate the viscoelastic properties of poly(N-isopropylacrylamide) (pNIPAM) hydrogels cross-linked with glutaraldehyde by means of small amplitude oscillatory and steady shear experiments in dependence on the frequency and shear rate. These properties are strongly influenced by the ratio of monomer and glutaraldehyde as a cross-linker. Due to the thermosensitivity of pNIPAM, the rheological properties of these hydrogels can be tuned by the temperature as an external stimulus. The experimentally obtained viscosities and linear viscoelastic moduli are analyzed by a schematic mode-coupling ansatz employing a rescaled F12-model.
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Affiliation(s)
- Joel Diaz Maier
- Institut für Chemie, Universität Rostock, 18051 Rostock, Germany
| | - Joachim Wagner
- Institut für Chemie, Universität Rostock, 18051 Rostock, Germany
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3
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Vaibhav V, Horbach J, Chaudhuri P. Rheological response of a glass-forming liquid having large bidispersity. SOFT MATTER 2022; 18:4427-4436. [PMID: 35638914 DOI: 10.1039/d2sm00326k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Using extensive numerical simulations, we investigate the flow behaviour of a model glass-forming binary mixture whose constituent particles have a large size ratio. The rheological response to applied shear is studied in the regime where the larger species are spatially predominant. We demonstrate that the macroscopic rigidity that emerges with increasing density occurs in the regime where the larger species undergo a glass transition while the smaller species continue to be highly diffusive. We analyse the interplay between the timescale imposed by the shear and the quiescent relaxation dynamics of the two species to provide a microscopic insight into the observed rheological response. Finally, by tuning the composition of the mixture, we illustrate that the systematic insertion of the smaller particles affects the rheology by lowering of viscosity of the system.
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Affiliation(s)
- Vinay Vaibhav
- The Institute of Mathematical Sciences, CIT Campus, Taramani, Chennai 600113, India.
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
| | - Jürgen Horbach
- Institut für Theoretische Physik II, Heinrich-Heine-Universität Düsseldorf, Universitätsstraß e 1, 40225 Düsseldorf, Germany.
| | - Pinaki Chaudhuri
- The Institute of Mathematical Sciences, CIT Campus, Taramani, Chennai 600113, India.
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
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4
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Luo C, Janssen LMC. Glassy dynamics of sticky hard spheres beyond the mode-coupling regime. SOFT MATTER 2021; 17:7645-7661. [PMID: 34373889 PMCID: PMC8900603 DOI: 10.1039/d1sm00712b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 08/04/2021] [Indexed: 06/13/2023]
Abstract
Sticky hard spheres, i.e., hard particles decorated with a short-ranged attractive interaction potential, constitute a relatively simple model with highly non-trivial glassy dynamics. The mode-coupling theory of the glass transition (MCT) offers a qualitative account of the complex reentrant dynamics of sticky hard spheres, but the predicted glass transition point is notoriously underestimated. Here we apply an improved first-principles-based theory, referred to as generalized mode-coupling theory (GMCT), to sticky hard spheres. This theoretical framework seeks to go beyond MCT by hierarchically expanding the dynamics in higher-order density correlation functions. We predict the phase diagrams from the first few levels of the GMCT hierarchy and the dynamics-related critical exponents, all of which are much closer to the empirical observations than MCT. Notably, the prominent reentrant glassy dynamics, the glass-glass transition, and the higher-order bifurcation singularity classes (A3 and A4) of sticky hard spheres are found to be preserved within GMCT at arbitrary order. Moreover, we demonstrate that when the hierarchical order of GMCT increases, the effect of the short-ranged attractive interactions becomes more evident in the dynamics. This implies that GMCT is more sensitive to subtle microstructural differences than MCT, and that the framework provides a promising first-principles approach to systematically go beyond the MCT regime.
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Affiliation(s)
- Chengjie Luo
- Department of Applied Physics, Eindhoven University of Technology, Eindhoven, The Netherlands.
| | - Liesbeth M C Janssen
- Department of Applied Physics, Eindhoven University of Technology, Eindhoven, The Netherlands.
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5
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Körber T, Pötzschner B, Krohn F, Rössler EA. Reorientational dynamics in highly asymmetric binary low-molecular mixtures-A quantitative comparison of dielectric and NMR spectroscopy results. J Chem Phys 2021; 155:024504. [PMID: 34266265 DOI: 10.1063/5.0056838] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Previously, we scrutinized the dielectric spectra of a binary glass former made by a low-molecular high-Tg component 2-(m-tertbutylphenyl)-2'-tertbutyl-9,9'-spirobi[9H]fluorene (m-TPTS; Tg = 350 K) and low-Tg tripropyl phosphate (TPP; Tg = 134 K) [Körber et al., Phys. Chem. Chem. Phys. 23, 7200 (2021)]. Here, we analyze nuclear magnetic resonance (NMR) spectra and stimulated echo decays of deuterated m-TPTS-d4 (2H) and TPP (31P) and attempt to understand the dielectric spectra in terms of component specific dynamics. The high-Tg component (α1) shows relaxation similar to that of neat systems, yet with some broadening upon mixing. This correlates with high-frequency broadening of the dielectric spectra. The low-Tg component (α2) exhibits highly stretched relaxations and strong dynamic heterogeneities indicated by "two-phase" spectra, reflecting varying fractions of fast and slow liquid-like reorienting molecules. Missing for the high-Tg component, such two-phase spectra are identified down to wTPP = 0.04, indicating that isotropic reorientation prevails in the rigid high-Tg matrix stretching from close to Tg TPP to Tg1 wTPP. This correlates with low-frequency broadening of the dielectric spectra. Two Tg values are defined: Tg1 (wTPP) displays a plasticizer effect, whereas Tg2 (wTPP) passes through a maximum, signaling extreme separation of the component dynamics at low wTPP. We suggest understanding the latter counter-intuitive feature by referring to a crossover from "single glass" to "double glass" scenario revealed by recent MD simulations. Analyses reveal that a second population of TPP molecules exists, which is associated with the dynamics of the high-Tg component. However, the fractions are lower than suggested by the dielectric spectra. We discuss this discrepancy considering the role of collective dynamics probed by dielectric but not by NMR spectroscopy.
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Affiliation(s)
- Thomas Körber
- Department of Inorganic Chemistry III and Northern Bavarian NMR Centre, University of Bayreuth, 95440 Bayreuth, Germany
| | - Björn Pötzschner
- Department of Inorganic Chemistry III and Northern Bavarian NMR Centre, University of Bayreuth, 95440 Bayreuth, Germany
| | - Felix Krohn
- Department of Macromolecular Chemistry and Bavarian Polymer Institute, University of Bayreuth, 95440 Bayreuth, Germany
| | - Ernst A Rössler
- Department of Inorganic Chemistry III and Northern Bavarian NMR Centre, University of Bayreuth, 95440 Bayreuth, Germany
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6
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Ikeda H, Miyazaki K, Yoshino H, Ikeda A. Multiple glass transitions and higher-order replica symmetry breaking of binary mixtures. Phys Rev E 2021; 103:022613. [PMID: 33736072 DOI: 10.1103/physreve.103.022613] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Accepted: 02/04/2021] [Indexed: 11/07/2022]
Abstract
We extend the replica liquid theory in order to describe the multiple glass transitions of binary mixtures with large size disparities, by taking into account the two-step replica symmetry breaking (2RSB). We determine the glass phase diagram of the mixture of large and small particles in the large-dimension limit where the mean-field theory becomes exact. When the size ratio of particles is beyond a critical value, the theory predicts three distinct glass phases; (i) the one-step replica symmetery breaking (1RSB) double glass where both components vitrify simultaneously, (ii) the 1RSB single glass where only large particles are frozen while small particles remain mobile, and (iii) a glass phase called the 2RSB double glass where both components vitrify simultaneously but with an energy landscape topography distinct from the 1RSB double glass.
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Affiliation(s)
- Harukuni Ikeda
- Graduate School of Arts and Sciences, The University of Tokyo 153-8902, Japan
| | | | - Hajime Yoshino
- Cybermedia Center, Osaka University, Toyonaka, Osaka 560-0043, Japan.,Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Atushi Ikeda
- Graduate School of Arts and Sciences, The University of Tokyo 153-8902, Japan
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7
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Ruscher C, Ciarella S, Luo C, Janssen LMC, Farago J, Baschnagel J. Glassy dynamics of a binary Voronoi fluid: a mode-coupling analysis. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:064001. [PMID: 33105111 DOI: 10.1088/1361-648x/abc4cc] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The binary Voronoi mixture is a fluid model whose interactions are derived from the Voronoi-Laguerre tessellation of the configurations of the system. The resulting interactions are local and many-body. Here we perform molecular-dynamics (MD) simulations of an equimolar mixture that is weakly polydisperse and additive. For the first time we study the structural relaxation of this mixture in the supercooled-liquid regime. From the simulations we determine the time- and temperature-dependent coherent and incoherent scattering functions for a large range of wave vectors, as well as the mean-square displacements of both particle species. We perform a detailed analysis of the dynamics by comparing the MD results with the first-principles-based idealized mode-coupling theory (MCT). To this end, we employ two approaches: fits to the asymptotic predictions of the theory, and fit-parameter-free binary MCT calculations based on static-structure-factor input from the simulations. We find that many-body interactions of the Voronoi mixture do not lead to strong qualitative differences relative to similar analyses carried out for simple liquids with pair-wise interactions. For instance, the fits give an exponent parameter λ ≈ 0.746 comparable to typical values found for simple liquids, the wavevector dependence of the Kohlrausch relaxation time is in good qualitative agreement with literature results for polydisperse hard spheres, and the MCT calculations based on static input overestimate the critical temperature, albeit only by a factor of about 1.2. This overestimation appears to be weak relative to other well-studied supercooled-liquid models such as the binary Kob-Andersen Lennard-Jones mixture. Overall, the agreement between MCT and simulation suggests that it is possible to predict several microscopic dynamic properties with qualitative, and in some cases near-quantitative, accuracy based solely on static two-point structural correlations, even though the system itself is inherently governed by many-body interactions.
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Affiliation(s)
- C Ruscher
- Université de Strasbourg, Institut Charles Sadron, CNRS-UPR22, 23 rue du Loess, BP 84047, 67034 Strasbourg Cedex 2, France
- Department of Physics and Astronomy and Quantum Matter Institute, University of British Columbia, Vancouver BC V6T 1Z1, Canada
| | - S Ciarella
- Theory of Polymers and Soft Matter, Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600MB Eindhoven, The Netherlands
| | - C Luo
- Theory of Polymers and Soft Matter, Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600MB Eindhoven, The Netherlands
| | - L M C Janssen
- Theory of Polymers and Soft Matter, Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600MB Eindhoven, The Netherlands
| | - J Farago
- Université de Strasbourg, Institut Charles Sadron, CNRS-UPR22, 23 rue du Loess, BP 84047, 67034 Strasbourg Cedex 2, France
| | - J Baschnagel
- Université de Strasbourg, Institut Charles Sadron, CNRS-UPR22, 23 rue du Loess, BP 84047, 67034 Strasbourg Cedex 2, France
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8
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Guevara-Pantoja FJ, Ruiz-Suárez JC. Nanovesicles drive a tunable dynamical arrest of microparticles. RSC Adv 2021; 11:24190-24195. [PMID: 35479007 PMCID: PMC9036661 DOI: 10.1039/d1ra04252a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 06/28/2021] [Indexed: 11/21/2022] Open
Abstract
Vitrification in a dilute colloidal system needs an asymmetric particle composition (a mixture of nano and micro colloids) to materialize. The volume fraction of the large particles increases (up to ≈0.58) driven by depletion forces produced by the smaller colloids. Such entropic forces are short-ranged and attractive. We found a different type of dynamical arrest in an extremely dilute asymmetric mixture of nanovesicles and polystyrene microparticles, where energy, instead of entropy, is the main protagonist to drive the arrest. Furthermore, when the vesicles go through the gel-fluid phase transition, the mean square displacements of the microparticles suffer a sudden splitting indicating a viscous jump. If the vesicles are doped with negatively charged lipids, particles and vesicles repel each other and the rheology of the mixture becomes athermal and Newtonian. Our findings are important to understand caging phenomena in biological systems, where diverse electrostatic distributions are present. A dynamical arrest in an extremely dilute asymmetric mixture of nanovesicles and polystyrene microparticles was discovered, where energy, instead of entropy, is the main mechanism to produce it.![]()
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9
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Körber T, Krohn F, Neuber C, Schmidt HW, Rössler EA. Reorientational dynamics of highly asymmetric binary non-polymeric mixtures – a dielectric spectroscopy study. Phys Chem Chem Phys 2021; 23:7200-7212. [DOI: 10.1039/d0cp06652d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two separated relaxations α1 and α2 with different temperature dependences are identified in the mixtures. They are attributed to the dynamics associated with the high-Tg (α1) and the low-Tg component (α2) with distinct Tg concentration dependences.
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Affiliation(s)
- Thomas Körber
- Department of Inorganic Chemistry III and Northern Bavarian NMR Centre
- University of Bayreuth
- 95440 Bayreuth
- Germany
| | - Felix Krohn
- Department of Macromolecular Chemistry and Bavarian Polymer Institute
- University of Bayreuth
- 95440 Bayreuth
- Germany
| | - Christian Neuber
- Department of Macromolecular Chemistry and Bavarian Polymer Institute
- University of Bayreuth
- 95440 Bayreuth
- Germany
| | - Hans-Werner Schmidt
- Department of Macromolecular Chemistry and Bavarian Polymer Institute
- University of Bayreuth
- 95440 Bayreuth
- Germany
| | - Ernst A. Rössler
- Department of Inorganic Chemistry III and Northern Bavarian NMR Centre
- University of Bayreuth
- 95440 Bayreuth
- Germany
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10
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Fullerton CJ, Berthier L. Glassy Behavior of Sticky Spheres: What Lies beyond Experimental Timescales? PHYSICAL REVIEW LETTERS 2020; 125:258004. [PMID: 33416397 DOI: 10.1103/physrevlett.125.258004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 10/21/2020] [Accepted: 11/23/2020] [Indexed: 06/12/2023]
Abstract
We use the swap Monte Carlo algorithm to analyze the glassy behavior of sticky spheres in equilibrium conditions at densities where conventional simulations and experiments fail to reach equilibrium, beyond predicted phase transitions and dynamic singularities. We demonstrate the existence of a unique ergodic region comprising all the distinct phases previously reported, except for a phase-separated region at strong adhesion. All structural and dynamic observables evolve gradually within this ergodic region, the physics evolving smoothly from well-known hard sphere glassy behavior at small adhesions and large densities, to a more complex glassy regime characterized by unusually broad distributions of relaxation timescales and length scales at large adhesions.
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Affiliation(s)
- Christopher J Fullerton
- Laboratoire Charles Coulomb (L2C), Université de Montpellier, CNRS, 34095 Montpellier, France
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, United Kingdom
| | - Ludovic Berthier
- Laboratoire Charles Coulomb (L2C), Université de Montpellier, CNRS, 34095 Montpellier, France
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
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11
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Voigtmann T, Siebenbürger M, Amann CP, Egelhaaf SU, Fritschi S, Krüger M, Laurati M, Mutch KJ, Samwer KH. Rheology of colloidal and metallic glass formers. Colloid Polym Sci 2020. [DOI: 10.1007/s00396-020-04654-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AbstractColloidal hard-sphere suspensions are convenient experimental models to understand soft matter, and also by analogy the structural-relaxation behavior of atomic or small-molecular fluids. We discuss this analogy for the flow and deformation behavior close to the glass transition. Based on a mapping of temperature to effective hard-sphere packing, the stress–strain curves of typical bulk metallic glass formers can be quantitatively compared with those of hard-sphere suspensions. Experiments on colloids give access to the microscopic structure under deformation on a single-particle level, providing insight into the yielding mechanisms that are likely also relevant for metallic glasses. We discuss the influence of higher-order angular signals in connection with non-affine particle rearrangements close to yielding. The results are qualitatively explained on the basis of the mode-coupling theory. We further illustrate the analogy of pre-strain dependence of the linear-elastic moduli using data on PS-PNiPAM suspensions.
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12
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Berntsen P, Ericsson T, Swenson J, Sjögren L. Complex modulus and compliance for airway smooth muscle cells. Phys Rev E 2020; 101:032410. [PMID: 32289912 DOI: 10.1103/physreve.101.032410] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Accepted: 01/24/2020] [Indexed: 11/07/2022]
Abstract
A cell can be described as a complex viscoelastic material with structural relaxations that is modulated by thermal and chemically nonequilibrium processes. Tissue morphology and function rely upon cells' physical responses to mechanical force. We measured the frequency-dependent mechanical relaxation response of adherent human airway smooth muscle cells under adenosine triphosphate (ATP) depletion and normal ATP conditions. The frequency dependence of the complex compliance J^{*} and modulus G^{*} was measured over the frequencies 10^{-1}<f<10^{3} Hz at selected temperatures between 4<T<54^{∘}C. Our results show characteristic relaxation features which can be interpreted by the mode-coupling theory (MCT) of viscoelastic liquids. We analyze the shape of the spectra in terms of a so-called A_{4} scenario with logarithmic scaling laws. Characteristic timescales τ_{β} and τ_{α} appear with corresponding energy barriers E_{β}≈(10-20)k_{B}T and E_{α}≈(20-30)k_{B}T. We demonstrate that cells are close to a glass transition. We find that the cell becomes softer around physiological temperatures, where its surface structure is more liquid-like with a plateau modulus around 0.1-0.8 kPa compared with the more solid-like interior cytoskeletal structures with a plateau modulus 1-15 kPa. Corresponding values for the viscosity are 10^{2}-10^{3} Pa s for the surface structures closer to the membrane and 10^{4}-10^{6} Pa s for the core cytoskeletal structures.
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Affiliation(s)
- Peter Berntsen
- Australian Research Council (ARC) Centre of Excellence in Advanced Molecular Imaging, Department of Chemistry and Physics, La Trobe Institute for Molecular Sciences, La Trobe University, Melbourne, Victoria 3086, Australia
| | - Thomas Ericsson
- Department of Mathematical Sciences, Chalmers University of Technology, and the University of Gothenburg, 41296 Göteborg, Sweden
| | - Jan Swenson
- Department of Physics, Chalmers University of Technology, 41296 Göteborg, Sweden
| | - Lennart Sjögren
- Department of Physics, University of Gothenburg, 41296 Göteborg, Sweden
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13
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Körber T, Minikejew R, Pötzschner B, Bock D, Rössler EA. Dynamically asymmetric binary glass formers studied by dielectric and NMR spectroscopy. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2019; 42:143. [PMID: 31773406 DOI: 10.1140/epje/i2019-11909-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 10/16/2019] [Indexed: 06/10/2023]
Abstract
We investigate the component dynamics in asymmetric binary glass formers. Focusing on the dielectric spectra of the high-Tg components m-tricresyl phosphate and quinaldine mixed with toluene as low-Tg component, the broadend spectra cannot be described by Kohlrausch or Cole-Davidson (CD) functions. Instead, we apply a generalized CD function which allows to control the width of the susceptibility independently of its high-frequency flank. The spectra show a common broadening and failure of the frequency-temperature superposition with increasing toluene concentration. This is confirmed by stimulated echo experiments showing an increased stretching of the probed orientational correlation function. In analogy to the definition of Tg, we consider "isodynamic points". For each component, a different but linear concentration dependence of 1/Tiso is revealed, indicating different time scales. Qualitativly, we do not find significant differences for the present mixtures with Tg-contrasts of 63-89K compared to those with larger Tg-contrast ( [Formula: see text] K): Whereas the high-Tg component shows relaxation features similar to those of neat glass formers, yet, with "atypical" weak relaxation broadening, the faster low-Tg component displays pronounced dynamic heterogeneities. This is supported by scrutinizing NMR relaxation data of several mixtures investigated previously as a function of concentration. A universal evolution of the dynamics of the high-Tg as well as the low-Tg component is suggested for mixtures with high [Formula: see text]Tg .
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Affiliation(s)
- Th Körber
- Universität Bayreuth, Anorganische Chemie III and Nordbayerisches NMR-Zentrum, D-95440, Bayreuth, Germany
| | - R Minikejew
- Universität Bayreuth, Anorganische Chemie III and Nordbayerisches NMR-Zentrum, D-95440, Bayreuth, Germany
| | - B Pötzschner
- Universität Bayreuth, Anorganische Chemie III and Nordbayerisches NMR-Zentrum, D-95440, Bayreuth, Germany
| | - D Bock
- Universität Bayreuth, Anorganische Chemie III and Nordbayerisches NMR-Zentrum, D-95440, Bayreuth, Germany
| | - E A Rössler
- Universität Bayreuth, Anorganische Chemie III and Nordbayerisches NMR-Zentrum, D-95440, Bayreuth, Germany.
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14
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Martinez-Sotelo E, Escobedo-Sánchez MA, Laurati M. Effect of size disparity on the structure and dynamics of the small component in concentrated binary colloidal mixtures. J Chem Phys 2019; 151:164504. [PMID: 31675880 DOI: 10.1063/1.5122306] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
We determined, using confocal microscopy, the structure and dynamics of the small component in concentrated binary colloidal mixtures with moderate and large size ratios and different compositions of Polymethyl methacrylate particles. We show that when increasing the content of small spheres at fixed total volume fraction, a transition in the local environment of the small particles is observed, from a mixed environment of other small and large particles to a local environment of only small particles. The transition is rather abrupt for moderate size ratios, while it becomes particularly broad for large size ratios. This can be associated with the improved ability of the small particles to pack in between the large particles for larger size ratios. The dynamics reflect the transition with an increase of the mobility observed at intermediate mixing. This increase becomes particularly pronounced for large size ratios, leading to diffusive dynamics of the small particles, in agreement with predictions of theories of the glass transition in binary hard-sphere mixtures. The composition at which the fastest dynamics are observed is apparently independent of the size ratio.
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Affiliation(s)
- E Martinez-Sotelo
- División de Ciencias e Ingenierás, Universidad de Guanajuato, Loma del Bosque 103, 37150 León, Mexico
| | - M A Escobedo-Sánchez
- Soft Matter Laboratory, Heinrich-Heine University, Universitätsstrasse 1, 42150 Düsseldorf, Germany
| | - M Laurati
- División de Ciencias e Ingenierás, Universidad de Guanajuato, Loma del Bosque 103, 37150 León, Mexico
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15
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Sentjabrskaja T, Jacob AR, Egelhaaf SU, Petekidis G, Voigtmann T, Laurati M. Binary colloidal glasses: linear viscoelasticity and its link to the microscopic structure and dynamics. SOFT MATTER 2019; 15:2232-2244. [PMID: 30794267 DOI: 10.1039/c8sm01349g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We study the relation between the microscopic structure and dynamics and the macroscopic rheological response of glass-forming colloidal suspensions, namely binary colloidal hard-sphere mixtures with large size asymmetry (1 : 5) that span a large range of mixture compositions close to the glass transition. The dynamical shear moduli are measured by oscillatory rheology and the structure and dynamics on the single-particle level by confocal microscopy. The data are compared with Brownian Dynamics simulations and predictions from mode-coupling theory based on the Percus-Yevick approximation. Experiments, simulations and theory consistently observe a strong decrease of the intermediate-frequency mechanical moduli combined with faster dynamics at intermediate mixing ratios and hence a non-monotonic dependence of these parameters but a localization of the large particles which decreases monotonically as the fraction of small particles is increased. We find that the Generalized-Stokes Einstein relation applied to the mean square displacements of the two components leads to a reasonable estimate of the shear moduli of the mixtures and hence links the rheological response to the particle dynamics which in turn reflects the microscopic structure.
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16
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Miyazaki R, Kawasaki T, Miyazaki K. Slow dynamics coupled with cluster formation in ultrasoft-potential glasses. J Chem Phys 2019; 150:074503. [PMID: 30795681 DOI: 10.1063/1.5086379] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We numerically investigate the slow dynamics of a binary mixture of ultrasoft particles interacting with the generalized Hertzian potential. If the softness parameter, α, is small, the particles at high densities start penetrating each other, form clusters, and eventually undergo the glass transition. We find multiple cluster-glass phases characterized by a different number of particles per cluster, whose boundary lines are sharply separated by the cluster size. Anomalous logarithmic slow relaxation of the density correlation functions is observed in the vicinity of these glass-glass phase boundaries, which hints the existence of the higher-order dynamical singularities predicted by the mode-coupling theory. Deeply in the cluster glass phases, it is found that the dynamics of a single particle is decoupled from that of the collective fluctuations.
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Müller N, Vogel M. Relation between concentration fluctuations and dynamical heterogeneities in binary glass-forming liquids: A molecular dynamics simulation study. J Chem Phys 2019; 150:064502. [DOI: 10.1063/1.5059355] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Niels Müller
- Institut für Festkörperphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany
| | - Michael Vogel
- Institut für Festkörperphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany
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18
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M. Zirdehi E, Varnik F. Non-monotonic effect of additive particle size on the glass transition in polymers. J Chem Phys 2019; 150:024903. [DOI: 10.1063/1.5063476] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Elias M. Zirdehi
- Interdisciplinary Centre for Advanced Materials Simulation (ICAMS), Ruhr-Universität Bochum, Universitätsstraße 150, 44801 Bochum, Germany
| | - Fathollah Varnik
- Interdisciplinary Centre for Advanced Materials Simulation (ICAMS), Ruhr-Universität Bochum, Universitätsstraße 150, 44801 Bochum, Germany
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19
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Varadarajan V, Dasgupta C, Ayappa KG. Influence of surface commensurability on the structure and relaxation dynamics of a confined monatomic fluid. J Chem Phys 2018; 149:064503. [DOI: 10.1063/1.5031422] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Affiliation(s)
- Vadhana Varadarajan
- Department of Chemical Engineering, Indian Institute of Science, Bangalore 560012, India
| | - Chandan Dasgupta
- Center for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | - K. G. Ayappa
- Department of Chemical Engineering, Indian Institute of Science, Bangalore 560012, India
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20
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Fernandez-Castanon J, Bomboi F, Sciortino F. Binding branched and linear DNA structures: From isolated clusters to fully bonded gels. J Chem Phys 2018; 148:025103. [PMID: 29331126 DOI: 10.1063/1.5011720] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The proper design of DNA sequences allows for the formation of well-defined supramolecular units with controlled interactions via a consecution of self-assembling processes. Here, we benefit from the controlled DNA self-assembly to experimentally realize particles with well-defined valence, namely, tetravalent nanostars (A) and bivalent chains (B). We specifically focus on the case in which A particles can only bind to B particles, via appropriately designed sticky-end sequences. Hence AA and BB bonds are not allowed. Such a binary mixture system reproduces with DNA-based particles the physics of poly-functional condensation, with an exquisite control over the bonding process, tuned by the ratio, r, between B and A units and by the temperature, T. We report dynamic light scattering experiments in a window of Ts ranging from 10 °C to 55 °C and an interval of r around the percolation transition to quantify the decay of the density correlation for the different cases. At low T, when all possible bonds are formed, the system behaves as a fully bonded network, as a percolating gel, and as a cluster fluid depending on the selected r.
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Affiliation(s)
- J Fernandez-Castanon
- Physics Department, Sapienza-Università di Roma, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - F Bomboi
- Physics Department, Sapienza-Università di Roma, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - F Sciortino
- Physics Department, Sapienza-Università di Roma, Piazzale Aldo Moro 5, 00185 Rome, Italy
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21
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Wang L, Mei B, Song J, Lu Y, An L. Structural relaxation and glass transition behavior of binary hard-ellipse mixtures. Sci China Chem 2018. [DOI: 10.1007/s11426-017-9151-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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22
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Zhang R, Schweizer KS. Microscopic Theory of Coupled Slow Activated Dynamics in Glass-Forming Binary Mixtures. J Phys Chem B 2018; 122:3465-3479. [DOI: 10.1021/acs.jpcb.7b10568] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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23
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Heckendorf D, Mutch KJ, Egelhaaf SU, Laurati M. Size-Dependent Localization in Polydisperse Colloidal Glasses. PHYSICAL REVIEW LETTERS 2017; 119:048003. [PMID: 29341743 DOI: 10.1103/physrevlett.119.048003] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Indexed: 06/07/2023]
Abstract
We have investigated concentrated suspensions of polydisperse hard spheres and have determined the dynamics and sizes of individual particles using confocal microscopy. With increasing concentration, the dynamics of the small and large particles start to differ. The large particles exhibit slower dynamics and stronger localization. Moreover, as the particle size increases, the local volume fraction ϕ_{loc} also increases. In the glass state, the localization length significantly decreases beyond ϕ_{loc}≈0.67. This suggests a link between local crowding and dynamical heterogeneities. However dynamical arrest of subpopulations seems not directly linked to a large value of ϕ_{loc}, indicating the importance of collective effects.
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Affiliation(s)
- D Heckendorf
- Condensed Matter Physics Laboratory, Heinrich Heine University, Universitätsstrasse 1, 40225 Düsseldorf, Germany
| | - K J Mutch
- Condensed Matter Physics Laboratory, Heinrich Heine University, Universitätsstrasse 1, 40225 Düsseldorf, Germany
| | - S U Egelhaaf
- Condensed Matter Physics Laboratory, Heinrich Heine University, Universitätsstrasse 1, 40225 Düsseldorf, Germany
| | - M Laurati
- Condensed Matter Physics Laboratory, Heinrich Heine University, Universitätsstrasse 1, 40225 Düsseldorf, Germany
- División de Ciencias e Ingenierías, Universidad de Guanajuato, Loma del Bosque 103, 37150 León, Mexico
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24
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Li CH, Luan YW, Han XJ, Li JG. Role of chemical short-range order in atomic dynamics decoupling. MOLECULAR SIMULATION 2017. [DOI: 10.1080/08927022.2017.1342121] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- C. H. Li
- Laboratory of Advanced Materials Solidification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, P.R. China
| | - Y. W. Luan
- Laboratory of Advanced Materials Solidification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, P.R. China
| | - X. J. Han
- Laboratory of Advanced Materials Solidification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, P.R. China
| | - J. G. Li
- Laboratory of Advanced Materials Solidification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, P.R. China
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Miyazaki R, Kawasaki T, Miyazaki K. Cluster Glass Transition of Ultrasoft-Potential Fluids at High Density. PHYSICAL REVIEW LETTERS 2016; 117:165701. [PMID: 27792362 DOI: 10.1103/physrevlett.117.165701] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Indexed: 06/06/2023]
Abstract
Using molecular dynamics simulation, we investigate the slow dynamics of a supercooled binary mixture of soft particles interacting with a generalized Hertzian potential. At low density, it displays typical slow dynamics near its glass transition temperature. At higher densities, particles bond together, forming clusters, and the clusters undergo the glass transition. The number of particles in a cluster increases one by one as the density increases. We demonstrate that there exist multiple cluster-glass phases characterized by a different number of particles per cluster, each of which is separated by distinct minima. Surprisingly, a so-called higher order singularity of the mode-coupling theory signaled by a logarithmic relaxation is observed in the vicinity of the boundaries between monomer and cluster glass phases. The system also exhibits rich and anomalous dynamics in the cluster glass phases, such as the decoupling of the self- and collective dynamics.
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Affiliation(s)
- Ryoji Miyazaki
- Department of Physics, Nagoya University, Nagoya 464-8602, Japan
| | - Takeshi Kawasaki
- Department of Physics, Nagoya University, Nagoya 464-8602, Japan
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26
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Spanner M, Höfling F, Kapfer SC, Mecke KR, Schröder-Turk GE, Franosch T. Splitting of the Universality Class of Anomalous Transport in Crowded Media. PHYSICAL REVIEW LETTERS 2016; 116:060601. [PMID: 26918973 DOI: 10.1103/physrevlett.116.060601] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Indexed: 06/05/2023]
Abstract
We investigate the emergence of subdiffusive transport by obstruction in continuum models for molecular crowding. While the underlying percolation transition for the accessible space displays universal behavior, the dynamic properties depend in a subtle nonuniversal way on the transport through narrow channels. At the same time, the different universality classes are robust with respect to introducing correlations in the obstacle matrix as we demonstrate for quenched hard-sphere liquids as underlying structures. Our results confirm that the microscopic dynamics can dominate the relaxational behavior even at long times, in striking contrast to glassy dynamics.
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Affiliation(s)
- Markus Spanner
- Institut für Theoretische Physik, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstraße 7, 91058 Erlangen, Germany
| | - Felix Höfling
- Fachbereich Mathematik und Informatik, Freie Universität Berlin, Arnimallee 6, 14195 Berlin, Germany
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstraße 3, 70569 Stuttgart, Germany, and IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
| | - Sebastian C Kapfer
- Institut für Theoretische Physik, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstraße 7, 91058 Erlangen, Germany
| | - Klaus R Mecke
- Institut für Theoretische Physik, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstraße 7, 91058 Erlangen, Germany
| | - Gerd E Schröder-Turk
- Murdoch University, School of Engineering and IT, Mathematics and Statistics, Murdoch, Western Australia 6150, Australia
| | - Thomas Franosch
- Institut für Theoretische Physik, Leopold-Franzens-Universität Innsbruck, Technikerstraße 21A, A-6020 Innsbruck, Austria
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27
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Pötzschner B, Mohamed F, Lichtinger A, Bock D, Rössler EA. Dynamics of asymmetric non-polymeric binary glass formers—A nuclear magnetic resonance and dielectric spectroscopy study. J Chem Phys 2015; 143:154506. [DOI: 10.1063/1.4932981] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- B. Pötzschner
- Experimentalphysik II, Universität Bayreuth, 95440 Bayreuth, Germany
| | - F. Mohamed
- Experimentalphysik II, Universität Bayreuth, 95440 Bayreuth, Germany
| | - A. Lichtinger
- Experimentalphysik II, Universität Bayreuth, 95440 Bayreuth, Germany
| | - D. Bock
- Experimentalphysik II, Universität Bayreuth, 95440 Bayreuth, Germany
| | - E. A. Rössler
- Experimentalphysik II, Universität Bayreuth, 95440 Bayreuth, Germany
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28
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Xu WS, Duan X, Sun ZY, An LJ. Glass formation in a mixture of hard disks and hard ellipses. J Chem Phys 2015; 142:224506. [DOI: 10.1063/1.4922379] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Wen-Sheng Xu
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA
| | - Xiaozheng Duan
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People’s Republic of China
| | - Zhao-Yan Sun
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People’s Republic of China
| | - Li-Jia An
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People’s Republic of China
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29
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Chaudhuri P, Hurtado PI, Berthier L, Kob W. Relaxation dynamics in a transient network fluid with competing gel and glass phases. J Chem Phys 2015; 142:174503. [DOI: 10.1063/1.4919645] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Pinaki Chaudhuri
- The Institute of Mathematical Sciences, C.I.T. Campus, Taramani, Chennai 600 113, India
| | - Pablo I. Hurtado
- Instituto Carlos I de Física Teórica y Computacional, and Departamento de Electromagnetismo y Física de la Materia, Universidad de Granada, Granada 18071, Spain
| | - Ludovic Berthier
- Laboratoire Charles Coulomb, UMR 5221, Université Montpellier and CNRS, 34095 Montpellier, France
| | - Walter Kob
- Laboratoire Charles Coulomb, UMR 5221, Université Montpellier and CNRS, 34095 Montpellier, France
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30
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Colmenero J. Are polymers standard glass-forming systems? The role of intramolecular barriers on the glass-transition phenomena of glass-forming polymers. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:103101. [PMID: 25634723 DOI: 10.1088/0953-8984/27/10/103101] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Traditionally, polymer melts have been considered archetypal glass-formers. This has been mainly due to the fact that these systems can easily be obtained as glasses by cooling from the melt, even at low cooling rates. However, the macromolecules, i.e. the structural units of polymer systems in general, are rather different from the standard molecules. They are long objects ('chains') made by repetition of a given chemical motif (monomer) and have intra-macromolecular barriers that limit their flexibility. The influence of these properties on, for instance, the glass-transition temperature of polymers, is a topic that has been widely studied by the polymer community almost from the early times of polymer science. However, in the framework of the glass-community, the relevant influence of intra-macromolecular barriers and chain connectivity on glass-transition phenomena of polymers has started to be recognized only recently. The aim of this review is to give an overview and to critically revise the results reported on this topic over the last years. From these results, it seems to be evident that there are two different mechanisms involved in the dynamic arrest in glass-forming polymers: (i) the intermolecular packing effects, which dominate the dynamic arrest of low molecular weight glass-forming systems; and (ii) the effect of intra-macromolecular barriers combined with chain connectivity. It has also been shown that the mode coupling theory (MCT) is a suitable theoretical framework to discuss these questions. The values found for polymers for the central MCT parameter--the so-called λ-exponent--are of the order of 0.9, clearly higher than the standard values (λ ≈ 0.7) found in systems where the dynamic arrest is mainly driven by packing effects ('standard' glass-formers). Within the MCT, this is a signature of the presence of two competing mechanisms of dynamic arrest, as it has been observed in short-ranged attractive colloids or two component mixtures with dynamic asymmetry. Moreover, recent MD-simulations of a 'bead-spring' polymer model, but including intra-macromolecular potential of different strengths, confirm that the high λ-values found in polymers are due to the effect of intra-macromolecular barriers. Although there are still open questions, these results allow to conclude that there is a fundamental difference between the nature of the glass transition in polymers and in simple (standard) glass-formers.
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Affiliation(s)
- J Colmenero
- Centro de Física de Materiales (CSIC-UPV/EHU) and Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain
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31
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Hendricks J, Capellmann R, Schofield AB, Egelhaaf SU, Laurati M. Different mechanisms for dynamical arrest in largely asymmetric binary mixtures. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 91:032308. [PMID: 25871111 DOI: 10.1103/physreve.91.032308] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Indexed: 06/04/2023]
Abstract
Using confocal microscopy we investigate binary colloidal mixtures with large size asymmetry, in particular the formation of dynamically arrested states of the large spheres. The volume fraction of the system is kept constant, and as the concentration of small spheres is increased we observe a series of transitions of the large spheres to different arrested states: an attractive glass, a gel, and an asymmetric glass. These states are distinguished by the degree of dynamical arrest and the amount of structural and dynamical heterogeneity. The transitions between two different arrested states occur through melting and the formation of a fluid state. While a space-spanning network of bonded particles is found in both arrested and fluid states, only arrested states are characterized by the presence of a space-spanning network of dynamically arrested particles.
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Affiliation(s)
- J Hendricks
- Condensed Matter Physics Laboratory, Heinrich-Heine University, Universitätsstr. 1, 40225 Düsseldorf, Germany
| | - R Capellmann
- Condensed Matter Physics Laboratory, Heinrich-Heine University, Universitätsstr. 1, 40225 Düsseldorf, Germany
| | - A B Schofield
- SUPA, School of Physics & Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - S U Egelhaaf
- Condensed Matter Physics Laboratory, Heinrich-Heine University, Universitätsstr. 1, 40225 Düsseldorf, Germany
| | - M Laurati
- Condensed Matter Physics Laboratory, Heinrich-Heine University, Universitätsstr. 1, 40225 Düsseldorf, Germany
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Frey S, Weysser F, Meyer H, Farago J, Fuchs M, Baschnagel J. Simulated glass-forming polymer melts: dynamic scattering functions, chain length effects, and mode-coupling theory analysis. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2015; 38:97. [PMID: 25715952 DOI: 10.1140/epje/i2015-15011-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Revised: 01/09/2015] [Accepted: 01/28/2015] [Indexed: 06/04/2023]
Abstract
We present molecular-dynamics simulations for a fully flexible model of polymer melts with different chain length N ranging from short oligomers (N = 4) to values near the entanglement length (N = 64). For these systems we explore the structural relaxation of the supercooled melt near the critical temperature T c of mode-coupling theory (MCT). Coherent and incoherent scattering functions are analyzed in terms of the idealized MCT. For temperatures T > T c we provide evidence for the space-time factorization property of the β relaxation and for the time-temperature superposition principle (TTSP) of the α relaxation, and we also discuss deviations from these predictions for T ≈ T c. For T larger than the smallest temperature where the TTSP holds we perform a quantitative analysis of the dynamics with the asymptotic MCT predictions for the late β regime. Within MCT a key quantity, in addition to T c, is the exponent parameter λ. For the fully flexible polymer models studied we find that λ is independent of N and has a value (λ = 0.735 ) typical of simple glass-forming liquids. On the other hand, the critical temperature increases with chain length toward an asymptotic value T c (∞) . This increase can be described by T c (∞) - T c(N) ∼ 1/N and may be interpreted in terms of the N dependence of the monomer density ρ, if we assume that the MCT glass transition is ruled by a soft-sphere-like constant coupling parameter Γ c = ρ c T c (-1/4), where ρ c is the monomer density at T c. In addition, we also estimate T c from a Hansen-Verlet-like criterion and MCT calculations based on structural input from the simulation. For our polymer model both the Hansen-Verlet criterion and the MCT calculations suggest T c to decrease with increasing chain length, in contrast to the direct analysis of the simulation data.
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Affiliation(s)
- S Frey
- Institut Charles Sadron, Université de Strasbourg, CNRS UPR 22, 23 rue du Loess, BP 84047, 67034, Strasbourg Cedex 2, France
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Schnyder SK, Spanner M, Höfling F, Franosch T, Horbach J. Rounding of the localization transition in model porous media. SOFT MATTER 2015; 11:701-711. [PMID: 25467065 DOI: 10.1039/c4sm02334j] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The generic mechanisms of anomalous transport in porous media are investigated by computer simulations of two-dimensional model systems. In order to bridge the gap between the strongly idealized Lorentz model and realistic models of porous media, two models of increasing complexity are considered: a cherry-pit model with hard-core correlations as well as a soft-potential model. An ideal gas of tracer particles inserted into these structures is found to exhibit anomalous transport which extends up to several decades in time. Also, the self-diffusion of the tracers becomes suppressed upon increasing the density of the systems. These phenomena are attributed to an underlying percolation transition. In the soft potential model the transition is rounded, since each tracer encounters its own critical density according to its energy. Therefore, the rounding of the transition is a generic occurrence in realistic, soft systems.
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Affiliation(s)
- Simon K Schnyder
- Institut für Theoretische Physik II: Weiche Materie, Heinrich Heine-Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany.
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34
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Xu WS, Sun ZY, An LJ. Relaxation dynamics in a binary hard-ellipse liquid. SOFT MATTER 2015; 11:627-634. [PMID: 25466776 DOI: 10.1039/c4sm02290d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Structural relaxation in binary hard spherical particles has been shown recently to exhibit a wealth of remarkable features when size disparity or mixture composition is varied. In this paper, we test whether or not similar dynamical phenomena occur in glassy systems composed of binary hard ellipses. We demonstrate via event-driven molecular dynamics simulation that a binary hard-ellipse mixture with an aspect ratio of two and moderate size disparity displays characteristic glassy dynamics upon increasing density in both the translational and the rotational degrees of freedom. The rotational glass transition density is found to be close to the translational one for the binary mixtures investigated. More importantly, we assess the influence of size disparity and mixture composition on the relaxation dynamics. We find that an increase of size disparity leads, both translationally and rotationally, to a speed up of the long-time dynamics in the supercooled regime so that both the translational and the rotational glass transition shift to higher densities. By increasing the number concentration of the small particles, the time evolution of both translational and rotational relaxation dynamics at high densities displays two qualitatively different scenarios, i.e., both the initial and the final part of the structural relaxation slow down for small size disparity, while the short-time dynamics still slows down but the final decay speeds up in the binary mixture with large size disparity. These findings are reminiscent of those observed in binary hard spherical particles. Therefore, our results suggest a universal mechanism for the influence of size disparity and mixture composition on the structural relaxation in both isotropic and anisotropic particle systems.
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Affiliation(s)
- Wen-Sheng Xu
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
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35
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Zaccarelli E, Liddle SM, Poon WCK. On polydispersity and the hard sphere glass transition. SOFT MATTER 2015; 11:324-330. [PMID: 25412138 DOI: 10.1039/c4sm02321h] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We investigate the dynamics of polydisperse hard spheres at high packing fractions ϕ. We use extensive numerical simulations based on an experimentally-realistic particle size distribution (PSD) and compare to commonly-used PSDs such as Gaussian or top hat distribution. We find that the mode of kinetic arrest depends on the PSD's shape and not only on its variance. For the experimentally-realistic PSD we find ageing dynamics even though the density correlators decay fully to zero for ϕ ≥ 0.59. We observe substantial decoupling of the dynamics of the smallest and largest particles. While the smallest particles remain diffusive in all our simulations, a power-law describes the largest-particle diffusion, suggesting an ideal arrest at ϕc ∼ 0.588. The latter is however averted just before ϕc, due to the presence of the mobile smallest particles. In addition, we identify that a partial aging mechanism is at work, whose effects are most pronounced for the largest particles. By comparing our results with recent experimental observations of ergodic behavior up to ϕ ∼ 0.6 in a hard-sphere system, we argue that this is an effect of polydispersity, which smears out the glass transition.
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Affiliation(s)
- Emanuela Zaccarelli
- CNR-ISC Uos Sapienza and Dipartimento di Fisica, Sapienza Università di Roma, P.le A. Moro 2, I-00185, Roma, Italy.
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36
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Gnan N, Das G, Sperl M, Sciortino F, Zaccarelli E. Multiple glass singularities and isodynamics in a core-softened model for glass-forming systems. PHYSICAL REVIEW LETTERS 2014; 113:258302. [PMID: 25554913 DOI: 10.1103/physrevlett.113.258302] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Indexed: 06/04/2023]
Abstract
We investigate the slow dynamics of a simple glass former whose interaction potential is the sum of a hard core and a square shoulder repulsion. According to mode coupling theory, the competition between the two repulsive length scales gives rise to a complex dynamic scenario: besides the fluid-glass line, the theory predicts a glass-glass line in the temperature-packing fraction plane with two end points. Interestingly, for critical values of the square-shoulder parameters, such end points can be accessed from the liquid phase. We verify, via extensive numerical simulations, the existence of both points through the observation of an unconventional subdiffusive/logarithmic dynamical behavior. Unexpectedly, we also discover that the simultaneous presence of two end points generates special loci in the state diagram along which the dynamics is identical at all length and time scales.
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Affiliation(s)
- Nicoletta Gnan
- CNR-ISC Uos Sapienza, Piazzale A. Moro 2, I-00185 Roma, Italy
| | - Gayatri Das
- Dipartimento di Fisica, Sapienza Universitá di Roma, Piazzale A. Moro 2, I-00185 Roma, Italy
| | - Matthias Sperl
- Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft-und Raumfahrt, 51170 Köln, Germany
| | - Francesco Sciortino
- Dipartimento di Fisica, Sapienza Universitá di Roma, Piazzale A. Moro 2, I-00185 Roma, Italy
| | - Emanuela Zaccarelli
- CNR-ISC Uos Sapienza, Piazzale A. Moro 2, I-00185 Roma, Italy and Dipartimento di Fisica, Sapienza Universitá di Roma, Piazzale A. Moro 2, I-00185 Roma, Italy
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37
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Abstract
Abstract
Focusing on metallic glasses as model systems, we review the features and mechanisms of the β-relaxations, which are intrinsic and universal to supercooled liquids and glasses, and demonstrate their importance in understanding many crucial unresolved issues in glassy physics and materials science, including glass transition phenomena, mechanical properties, shear-banding dynamics and deformation mechanisms, diffusion and the breakdown of the Stokes–Einstein relation as well as crystallization and stability of glasses. We illustrate that it is an attractive prospect to incorporate these insights into the design of new glassy materials with extraordinary properties. We also outline important questions regarding the nature of β-relaxations and highlight some emerging research directions in this still-evolving field.
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Affiliation(s)
- Hai Bin Yu
- Physikalisches Institut, Universität Göttingen, D-37077 Göttingen, Germany
| | - Wei Hua Wang
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Hai Yang Bai
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Konrad Samwer
- Physikalisches Institut, Universität Göttingen, D-37077 Göttingen, Germany
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38
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Khairy Y, Alvarez F, Arbe A, Colmenero J. Applicability of mode-coupling theory to polyisobutylene: a molecular dynamics simulation study. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 88:042302. [PMID: 24229167 DOI: 10.1103/physreve.88.042302] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Indexed: 06/02/2023]
Abstract
The applicability of Mode Coupling Theory (MCT) to the glass-forming polymer polyisobutylene (PIB) has been explored by using fully atomistic molecular dynamics simulations. MCT predictions for the so-called asymptotic regime have been successfully tested on the dynamic structure factor and the self-correlation function of PIB main-chain carbons calculated from the simulated cell. The factorization theorem and the time-temperature superposition principle are satisfied. A consistent fitting procedure of the simulation data to the MCT asymptotic power-laws predicted for the α-relaxation regime has delivered the dynamic exponents of the theory-in particular, the exponent parameter λ-the critical non-ergodicity parameters, and the critical temperature T(c). The obtained values of λ and T(c) agree, within the uncertainties involved in both studies, with those deduced from depolarized light scattering experiments [A. Kisliuk et al., J. Polym. Sci. Part B: Polym. Phys. 38, 2785 (2000)]. Both, λ and T(c)/T(g) values found for PIB are unusually large with respect to those commonly obtained in low molecular weight systems. Moreover, the high T(c)/T(g) value is compatible with a certain correlation of this parameter with the fragility in Angell's classification. Conversely, the value of λ is close to that reported for real polymers, simulated "realistic" polymers and simple polymer models with intramolecular barriers. In the framework of the MCT, such finding should be the signature of two different mechanisms for the glass-transition in real polymers: intermolecular packing and intramolecular barriers combined with chain connectivity.
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Affiliation(s)
- Y Khairy
- Centro de Física de Materiales (CSIC-UPV/EHU) - Materials Physics Center (MPC), Paseo Manuel de Lardizabal 5, 20018 San Sebastián, Spain
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39
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Xu WS, Sun ZY, An LJ. Structure, compressibility factor, and dynamics of highly size-asymmetric binary hard-disk liquids. J Chem Phys 2012; 137:104509. [DOI: 10.1063/1.4751546] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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40
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Yu HB, Samwer K, Wu Y, Wang WH. Correlation between β relaxation and self-diffusion of the smallest constituting atoms in metallic glasses. PHYSICAL REVIEW LETTERS 2012; 109:095508. [PMID: 23002852 DOI: 10.1103/physrevlett.109.095508] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Indexed: 06/01/2023]
Abstract
In multicomponent metallic glasses, we demonstrate that diffusion and secondary (β) relaxation are closely related. The diffusion motion of the smallest constituting atoms takes place within the temperature and time regimes where the β relaxations are activated, and, in particular, the two processes have similar activation energies. We suggest cooperative stringlike atomic motion plays an important role in both processes. This finding provides additional insights into the structural origin of the β relaxations as well as the mechanisms of diffusions in metallic glasses.
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Affiliation(s)
- H B Yu
- I. Physikalisches Institut, Universität Göttingen, D-37077 Göttingen, Germany.
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41
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Busselez R, Arbe A, Cerveny S, Capponi S, Colmenero J, Frick B. Component dynamics in polyvinylpyrrolidone concentrated aqueous solutions. J Chem Phys 2012; 137:084902. [DOI: 10.1063/1.4746020] [Citation(s) in RCA: 33] [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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42
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Gallo P, Rovere M, Chen SH. Water confined in MCM-41: a mode coupling theory analysis. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:064109. [PMID: 22277593 DOI: 10.1088/0953-8984/24/6/064109] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
In this paper we analyze molecular dynamics simulation results on supercooled water in a MCM-41 pore in order to test the mode coupling theory. A layer analysis must be performed for water in the pore in order to exclude the contribution of water bound to the strongly hydrophilic surface. Upon supercooling a range of temperatures is reached where the liquid follows the mode coupling theory. From the power law behavior of the relaxation times extracted from the Kohlrausch-William-Watts fit to the self-intermediate scattering function, we obtain the crossover temperature T(C) and the γ exponent of the theory. The time-temperature superposition principle is also satisfied. A fit to the von Schweidler law yields a coefficient b from which all the other parameters of the theory have been calculated. In particular, we obtained the same value of γ as extracted from the power law fit to the relaxation times, in agreement with the requirements of the theory. For very low temperatures, the mode coupling theory no longer holds as hopping processes intervene and water turns its behavior to that of a strong liquid.
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Affiliation(s)
- P Gallo
- Dipartimento di Fisica, Università Roma Tre, Via della Vasca Navale 84, 00146 Roma, Italy.
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43
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Gallo P, Rovere M. Lennard-Jones binary mixture in disordered matrices: exploring the mode coupling scenario at increasing confinement. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:234118. [PMID: 21613712 DOI: 10.1088/0953-8984/23/23/234118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We present results of molecular dynamics simulations performed on a Lennard-Jones liquid binary mixture confined in matrices of soft spheres at increasing packing fraction. We study the dynamical properties of the liquid at a given density upon supercooling. Our aim is to test the validity of the mode coupling theory in predicting the behaviour of the glass forming liquid when it is under confinement in a disordered matrix. We use two different methods to build up the confining environment. We focus in particular on the behaviour of the single particle density correlators. We find a close agreement with the mode coupling theory at least for all the range of packing fractions examined. Discrepancies between the theory and the computer simulation results can be attributed to hopping effects which are more important at increasing confinement.
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Affiliation(s)
- P Gallo
- Dipartimento di Fisica, Università Roma Tre, Via della Vasca Navale 84, I-00146 Roma, Italy.
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44
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Kurzidim J, Coslovich D, Kahl G. Dynamic arrest of colloids in porous environments: disentangling crowding and confinement. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:234122. [PMID: 21613709 DOI: 10.1088/0953-8984/23/23/234122] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Using numerical simulations we study the slow dynamics of a colloidal hard-sphere fluid adsorbed in a matrix of disordered hard-sphere obstacles. We calculate separately the contributions to the single-particle dynamic correlation functions due to free and trapped particles. The separation is based on a Delaunay tessellation to partition the space accessible to the centres of fluid particles into percolating and disconnected voids. We find that the trapping of particles into disconnected voids of the matrix is responsible for the appearance of a nonzero long-time plateau in the single-particle intermediate scattering functions of the full fluid. The subdiffusive exponent z, obtained from the logarithmic derivative of the mean squared displacement, is essentially unaffected by the motion of trapped particles: close to the percolation transition, we determined z approximately = 0.5 for both the full fluid and the particles moving in the percolating void. Notably, the same value of z is found in single-file diffusion and is also predicted by mode-coupling theory along the diffusion-localization line. We also reveal subtle effects of dynamic heterogeneity in both the free and the trapped component of the fluid particles, and discuss microscopic mechanisms that contribute to this phenomenon.
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Affiliation(s)
- Jan Kurzidim
- Institut für Theoretische Physik and Center for Computational Materials Science, Technische Universität Wien, Wien, Austria.
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45
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Kim K, Miyazaki K, Saito S. Slow dynamics, dynamic heterogeneities, and fragility of supercooled liquids confined in random media. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:234123. [PMID: 21613691 DOI: 10.1088/0953-8984/23/23/234123] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Using molecular dynamics simulations, we study the slow dynamics of supercooled liquids confined in a random matrix of immobile obstacles. We study the dynamical crossover from glass-like to Lorentz-gas-like behavior in terms of the density correlation function, the mean square displacement, the nonlinear dynamic susceptibility, the non-gaussian parameter, and the fragility. We find the cooperative and spatially heterogeneous dynamics to be suppressed as the obstacle density increases, leading to a more Arrhenius-like behavior in the temperature dependence of the relaxation time. Our findings are qualitatively consistent with the results of recent experimental and numerical studies for various classes of spatially heterogeneous systems. We also investigate the dependence of the dynamics of mobile particles on the protocol used to generate the random matrix. A re-entrant transition from the arrested phase to the liquid phase as the mobile particle density increases is observed for a class of protocols. This re-entrance is explained in terms of the distribution of the volume of the voids that are available to the mobile particles.
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Affiliation(s)
- Kang Kim
- Institute for Molecular Science, Okazaki 444-8585, Japan.
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46
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Moreno AJ, Arbe A, Colmenero J. Structure and Dynamics of Self-Assembled Comb Copolymers: Comparison between Simulations of a Generic Model and Neutron Scattering Experiments. Macromolecules 2011. [DOI: 10.1021/ma102545n] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Angel J. Moreno
- Centro de Física de Materiales (CSIC, UPV-EHU) and Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain
| | - Arantxa Arbe
- Centro de Física de Materiales (CSIC, UPV-EHU) and Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain
| | - Juan Colmenero
- Centro de Física de Materiales (CSIC, UPV-EHU) and Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain
- Donostia International Physics Center, Paseo Manuel de Lardizabal 4, E-20018 San Sebastián, Spain
- Departamento de Física de Materiales, Universidad del País Vasco (UPV-EHU), Apartado 1072, E-20080 San Sebastián, Spain
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47
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Krakoviack V. Statistical mechanics of homogeneous partly pinned fluid systems. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 82:061501. [PMID: 21230672 DOI: 10.1103/physreve.82.061501] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2010] [Indexed: 05/30/2023]
Abstract
The homogeneous partly pinned fluid systems are simple models of a fluid confined in a disordered porous matrix obtained by arresting randomly chosen particles in a one-component bulk fluid or one of the two components of a binary mixture. In this paper, their configurational properties are investigated. It is shown that a peculiar complementarity exists between the mobile and immobile phases, which originates from the fact that the solid is prepared in presence of and in equilibrium with the adsorbed fluid. Simple identities follow, which connect different types of configurational averages, either relative to the fluid-matrix system or to the bulk fluid from which it is prepared. Crucial simplifications result for the computation of important structural quantities, both in computer simulations and in theoretical approaches. Finally, possible applications of the model in the field of dynamics in confinement or in strongly asymmetric mixtures are suggested.
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Affiliation(s)
- Vincent Krakoviack
- Laboratoire de Chimie, École Normale Supérieure de Lyon, 46 Allée d'Italie, 69364 Lyon Cedex 07, France
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48
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Kurita R, Weeks ER. Glass transition of two-dimensional binary soft-disk mixtures with large size ratios. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 82:041402. [PMID: 21230272 DOI: 10.1103/physreve.82.041402] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2009] [Revised: 08/19/2010] [Indexed: 05/30/2023]
Abstract
We simulate binary soft-disk systems in two dimensions and investigate how the dynamics slow as the area fraction is increased toward the glass transition. The "fragility" quantifies how sensitively the relaxation time scale depends on the area fraction, and the fragility strongly depends on the composition of the mixture. We confirm prior results for mixtures of particles with similar sizes, where the ability to form small crystalline regions correlates with fragility. However, for mixtures with particle size ratios above 1.4, we find that the fragility is not correlated with structural ordering, but rather with the spatial distribution of large particles. The large particles have slower motion than the small particles and act as confining "walls" which slow the motion of nearby small particles. The rearrangement of these confining structures governs the lifetime of dynamical heterogeneity, that is, how long local regions exhibit anomalously fast or slow behavior. The strength of the confinement effect is correlated with the fragility and also influences the aging behavior of glassy systems.
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Affiliation(s)
- Rei Kurita
- Department of Physics, Emory University, Atlanta, Georgia 30322, USA
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49
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Kurzidim J, Coslovich D, Kahl G. Impact of random obstacles on the dynamics of a dense colloidal fluid. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 82:041505. [PMID: 21230280 DOI: 10.1103/physreve.82.041505] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2010] [Indexed: 05/30/2023]
Abstract
Using molecular dynamics simulations we study the slow dynamics of a colloidal fluid annealed within a matrix of obstacles quenched from an equilibrated colloidal fluid. We choose all particles to be of the same size and to interact as hard spheres, thus retaining all features of the porous confinement while limiting the control parameters to the packing fraction of the matrix, φ(m), and that of the fluid, φ(f). We conduct detailed investigations on several dynamic properties, including the tagged-particle and collective intermediate scattering functions, the mean-squared displacement, and the van Hove function. We show the confining obstacles to profoundly impact the relaxation pattern of various quantifiers pertinent to the fluid. Varying the type of quantifier (tagged-particle or collective) as well as φ(m) and φ(f), we unveil both discontinuous and continuous arrest scenarios. Furthermore, we discover subdiffusive behavior and demonstrate its close connection to the matrix structure. Our findings partly confirm the various predictions of a recent extension of mode-coupling theory to the quenched-annealed protocol.
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Affiliation(s)
- Jan Kurzidim
- Institut für Theoretische Physik and CMS, Technische Universität Wien, Wiedner Hauptstraße 8-10, 1040 Wien, Austria
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50
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Bartsch A, Rätzke K, Meyer A, Faupel F. Dynamic arrest in multicomponent glass-forming alloys. PHYSICAL REVIEW LETTERS 2010; 104:195901. [PMID: 20866980 DOI: 10.1103/physrevlett.104.195901] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Revised: 04/22/2010] [Indexed: 05/13/2023]
Abstract
We report radiotracer diffusivities in a Pd43Cu27Ni10P20 melt, presenting for the first time a complete set of data for all components over the whole relevant temperature range. While a vast decoupling of more than 4 orders of magnitude is observed between the diffusivity of Pd and of the smaller components, at the glass transition temperature Tg, the diffusivities of all components merge close to the critical temperature Tc of mode coupling theory. For Pd, the Stokes-Einstein relation holds in the whole range investigated encompassing more than 14 orders of magnitude suggesting the formation of a slow subsystem as a key to glass formation in systems with dynamic asymmetry.
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Affiliation(s)
- Alexander Bartsch
- Institut für Materialwissenschaft-Materialverbunde, Technische Fakultät, Christian-Albrechts-Universität zu Kiel, Kaiserstrasse 2, D-24143 Kiel, Germany
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