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Srinivasan H, Sharma VK, García Sakai V, Mitra S. Nature of Subdiffusion Crossover in Molecular and Polymeric Glassformers. PHYSICAL REVIEW LETTERS 2024; 132:058202. [PMID: 38364148 DOI: 10.1103/physrevlett.132.058202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 11/21/2023] [Accepted: 01/03/2024] [Indexed: 02/18/2024]
Abstract
A crossover from a non-Gaussian to Gaussian subdiffusion has been observed ubiquitously in various polymeric and molecular glassformers. We have developed a framework that generalizes the fractional Brownian motion model to incorporate non-Gaussian features by introducing a jump kernel. We illustrate that the non-Gaussian fractional Brownian motion model accurately characterizes the subdiffusion crossover. From the solutions of the non-Gaussian fractional Brownian motion model, we gain insights into the nature of van Hove self-correlation in non-Gaussian subdiffusive regime, which is found to exhibit exponential tails, providing first such experimental evidence in molecular glassformers. The validity of the model is supported by comparison with incoherent quasielastic neutron scattering data obtained from several molecular and polymeric glassformers.
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Affiliation(s)
- H Srinivasan
- Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
| | - V K Sharma
- Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
| | - V García Sakai
- ISIS Neutron and Muon Centre, Rutherford Appleton Laboratory, Didcot, United Kingdom
| | - S Mitra
- Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
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Khairy Y, Alvarez F, Arbe A, Colmenero J. Disentangling Self-Atomic Motions in Polyisobutylene by Molecular Dynamics Simulations. Polymers (Basel) 2021; 13:polym13040670. [PMID: 33672368 PMCID: PMC7927061 DOI: 10.3390/polym13040670] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 02/08/2021] [Accepted: 02/17/2021] [Indexed: 01/16/2023] Open
Abstract
We present fully atomistic molecular dynamics simulations on polyisobutylene (PIB) in a wide temperature range above the glass transition. The cell is validated by direct comparison of magnitudes computed from the simulation and measured by neutron scattering on protonated samples reported in previous works. Once the reliability of the simulation is assured, we exploit the information in the atomic trajectories to characterize the dynamics of the different kinds of atoms in PIB. All of them, including main-chain carbons, show a crossover from Gaussian to non-Gaussian behavior in the intermediate scattering function that can be described in terms of the anomalous jump diffusion model. The full characterization of the methyl-group hydrogen motions requires accounting for rotational motions. We show that the usually assumed statistically independence of rotational and segmental motions fails in this case. We apply the rotational rate distribution model to correlation functions calculated for the relative positions of methyl-group hydrogens with respect to the carbon atom at which they are linked. The contributions to the vibrational density of states are also discussed. We conclude that methyl-group rotations are coupled with the main-chain dynamics. Finally, we revise in the light of the simulations the hypothesis and conclusions made in previously reported neutron scattering investigations on protonated samples trying to address the origin of the dielectric β-process.
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Affiliation(s)
- Yasmin Khairy
- Physics Department, Faculty of Science, Zagazig University, Zagazig 44519, Egypt;
- Centro de Física de Materiales (CSIC, UPV/EHU), Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain; (F.A.); (A.A.)
| | - Fernando Alvarez
- Centro de Física de Materiales (CSIC, UPV/EHU), Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain; (F.A.); (A.A.)
- Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain
- Departamento de Polímeros y Materiales Avanzados: Física, Química y Tecnología (UPV/EHU), Apartado 1072, E-20080 San Sebastián, Spain
| | - Arantxa Arbe
- Centro de Física de Materiales (CSIC, UPV/EHU), Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain; (F.A.); (A.A.)
- Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain
| | - Juan Colmenero
- Centro de Física de Materiales (CSIC, UPV/EHU), Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain; (F.A.); (A.A.)
- Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain
- Departamento de Polímeros y Materiales Avanzados: Física, Química y Tecnología (UPV/EHU), Apartado 1072, E-20080 San Sebastián, Spain
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, E-20018 San Sebastián, Spain
- Correspondence:
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Malfait B, Pouessel A, Jani A, Morineau D. Extension and Limits of Cryoscopy for Nanoconfined Solutions. J Phys Chem Lett 2020; 11:5763-5769. [PMID: 32590897 DOI: 10.1021/acs.jpclett.0c01564] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
This work investigates the phase behavior of aqueous solutions of glycerol confined in MCM-41 and SBA-15 nanoporous matrixes by calorimetry. Limitations due to overfilling and eutectic freezing are prevented by the absence of an external liquid reservoir and by the glass-forming property of glycerol. Consequently, the stability of nanoconfined ice in equilibrium with aqueous solutions is studied over a wide range of compositions. In confinement, a large temperature depression of the liquidus line is observed. A thermodynamic model accounting simultaneously for the cryoscopic and the Gibbs-Thomson effects gives a consistent view of the phase diagram for large pores (Rp = 4.15 nm). For smaller pores (Rp = 1.8 nm), it reveals that the water activity strongly deviates from the bulk solution with the same composition, indicating the possible role of concentration heterogeneities in determining the onset of ice freezing in strongly nanoconfined solutions.
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Affiliation(s)
- Benjamin Malfait
- Institute of Physics of Rennes, CNRS-University of Rennes 1, UMR 6251, F-35042 Rennes, France
| | - Alban Pouessel
- Institute of Physics of Rennes, CNRS-University of Rennes 1, UMR 6251, F-35042 Rennes, France
| | - Aîcha Jani
- Institute of Physics of Rennes, CNRS-University of Rennes 1, UMR 6251, F-35042 Rennes, France
| | - Denis Morineau
- Institute of Physics of Rennes, CNRS-University of Rennes 1, UMR 6251, F-35042 Rennes, France
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Boulé R, Roiland C, Bataille T, Le Pollés L, Audebrand N, Ghoufi A. Anomalous Dynamics of a Nanoconfined Gas in a Soft Metal-Organics Framework. J Phys Chem Lett 2019; 10:1698-1708. [PMID: 30913385 DOI: 10.1021/acs.jpclett.9b00421] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Dynamics of confined molecules within porous materials is equally important as local structural order, and it is necessary to quantify it and to reveal the microscopic mechanisms ruling it for better control of adsorption applications. In this study, molecular dynamics simulations were carried out to investigate the translational and the rotational dynamics of methanol trapped into the flexible NH2-MIL-53(Al) metal-organics framework (MOF). Indeed, atomistic simulation is nowadays a relevant tool to explore matter at the nanoscale. Very recently it has been shown that the NH2-MIL-53(Al) MOF material was capable to undergo a reversible structural transition (breathing phenomenon) by combining adsorption and thermal stimuli. This flexibility can drastically affect the dynamics of confined molecules and therefore the successful conduct of adsorption applications such as gas storage and separation. Rotational and translational dynamics of confined methanol through nanoporous flexible NH2-MIL-53(Al) MOF were then deeply investigated by exploring a broad range of dynamical properties to extract the molecular mechanisms ruling them. This study allowed us to shed light on the interplay of dynamics of confined fluids and flexibility of porous material and to highlight the physical insights in diffusion mechanisms of confined molecules. Anomalous translational diffusion was evidenced due to a dynamical heterogeneity caused by a combination of a localized dynamics at the subnanometric scale and translational jumps between nanodomains in a zigzag scheme between the hydroxide group of the NH2-MIL-53(Al). Actually, the non-Fickian dynamics of methanol is the result of the specific host-guest interactions and the MOF flexibility involving the pore opening. Eventually, decoupling between both rotational and translational dynamics related to breaking in the Stokes-Einstein relation was highlighted.
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Affiliation(s)
- Roald Boulé
- Univ Rennes, CNRS, ENSCR, ISCR (Institut des Sciences Chimiques de Rennes) - UMR 6226 , F-35000 Rennes , France
| | - Claire Roiland
- Univ Rennes, CNRS, ENSCR, ISCR (Institut des Sciences Chimiques de Rennes) - UMR 6226 , F-35000 Rennes , France
| | - Thierry Bataille
- Univ Rennes, CNRS, ENSCR, ISCR (Institut des Sciences Chimiques de Rennes) - UMR 6226 , F-35000 Rennes , France
| | - Laurent Le Pollés
- Univ Rennes, CNRS, ENSCR, ISCR (Institut des Sciences Chimiques de Rennes) - UMR 6226 , F-35000 Rennes , France
| | - Nathalie Audebrand
- Univ Rennes, CNRS, ENSCR, ISCR (Institut des Sciences Chimiques de Rennes) - UMR 6226 , F-35000 Rennes , France
| | - Aziz Ghoufi
- Univ Rennes, CNRS, IPR (Institut de Physique de Rennes) - UMR 6251 , F-35000 Rennes , France
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Abstract
Nowadays powerful X-ray sources like synchrotrons and free-electron lasers are considered as ultimate tools for probing microscopic properties in materials. However, the correct interpretation of such experiments requires a good understanding on how the beam affects the properties of the sample, knowledge that is currently lacking for intense X-rays. Here we use X-ray photon correlation spectroscopy to probe static and dynamic properties of oxide and metallic glasses. We find that although the structure does not depend on the flux, strong fluxes do induce a non-trivial microscopic motion in oxide glasses, whereas no such dependence is found for metallic glasses. These results show that high fluxes can alter dynamical properties in hard materials, an effect that needs to be considered in the analysis of X-ray data but which also gives novel possibilities to study materials properties since the beam can not only be used to probe the dynamics but also to pump it.
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Busselez R, Pezeril T, Gusev VE. Structural heterogeneities at the origin of acoustic and transport anomalies in glycerol glass-former. J Chem Phys 2015; 140:234505. [PMID: 24952550 DOI: 10.1063/1.4883504] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
By means of large scale molecular dynamics simulations, we explore mesoscopic properties of prototypical glycerol glass-former above and below the glass transition. The model used, in excellent agreement with various experimental techniques, permits to carefully study the structure and the vibrational dynamics. We find that a medium range order is present in glycerol glass-former and arises from hydrogen bond network extension. The characteristic size of the structural heterogeneities is related to the anomalous properties of acoustic vibrations (Rayleigh scattering, "mode softening," and Boson Peak) in the glassy state. Finally the characteristic size of these heterogeneities, nearly constant in temperature, is also connected to the cross-over between structural relaxation and diffusion in liquid glycerol.
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Affiliation(s)
- Rémi Busselez
- Institut des Molécules et Matériaux du Mans UMR-CNRS 6283, Université du Maine, Le Mans, France
| | - Thomas Pezeril
- Institut des Molécules et Matériaux du Mans UMR-CNRS 6283, Université du Maine, Le Mans, France
| | - Vitalyi E Gusev
- Laboratoire d'Acoustique de l'Université du Maine, UMR-CNRS 6613 Université du Maine, Le Mans, France
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Busselez R, Cerclier CV, Ndao M, Ghoufi A, Lefort R, Morineau D. Discotic columnar liquid crystal studied in the bulk and nanoconfined states by molecular dynamics simulation. J Chem Phys 2014; 141:134902. [DOI: 10.1063/1.4896052] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Rémi Busselez
- Institut de Physique de Rennes, CNRS UMR 6251, Université de Rennes 1, 35042 Rennes, France
- Institut des Molécules et des Matériaux du Mans, UMR-CNRS 6283 Université du Maine, Avenue Olivier Messiaen 72085 Le Mans Cedex 9, France
| | - Carole V. Cerclier
- Institut de Physique de Rennes, CNRS UMR 6251, Université de Rennes 1, 35042 Rennes, France
- Institut des Matériaux de Nantes (IMN), UMR-CNRS 6502, 2 rue de la Houssiniere, BP32229, 44322 Nantes cedex3, France
| | - Makha Ndao
- Institut de Physique de Rennes, CNRS UMR 6251, Université de Rennes 1, 35042 Rennes, France
- Institut de Chimie de Clermont-Ferrand (ICCF) - UMR-CNRS 6296, Université Blaise Pascal, Campus des Cézeaux, 63171 Aubiere cedex, France
| | - Aziz Ghoufi
- Institut de Physique de Rennes, CNRS UMR 6251, Université de Rennes 1, 35042 Rennes, France
| | - Ronan Lefort
- Institut de Physique de Rennes, CNRS UMR 6251, Université de Rennes 1, 35042 Rennes, France
| | - Denis Morineau
- Institut de Physique de Rennes, CNRS UMR 6251, Université de Rennes 1, 35042 Rennes, France
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