1
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Kim EC, Chun DJ, Park CB, Sung BJ. Machine learning predicts the glass transition of two-dimensional colloids besides medium-range crystalline order. Phys Rev E 2023; 108:044602. [PMID: 37978710 DOI: 10.1103/physreve.108.044602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Accepted: 08/10/2023] [Indexed: 11/19/2023]
Abstract
We employ only the positions of colloidal particles and construct machine learning (ML) models to test the presence of structural order in glass transition for two kinds of two-dimensional (2D) colloids: 2D polydisperse colloids (PC) with medium-range crystalline order (MRCO) and 2D binary colloids (BC) without MRCO. ML models predict the glass transition of 2D colloids successfully without any information on MRCO. Even certain ML models trained with BC predict the glass transition of PC successfully, thus suggesting that universal structural characteristics would exist besides MRCO.
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Affiliation(s)
- Eun Cheol Kim
- Department of Chemistry, Sogang University, Seoul 04107, Republic of Korea
| | - Dong Jae Chun
- Department of Chemistry, Sogang University, Seoul 04107, Republic of Korea
| | - Chung Bin Park
- Department of Chemistry, Sogang University, Seoul 04107, Republic of Korea
| | - Bong June Sung
- Department of Chemistry, Sogang University, Seoul 04107, Republic of Korea
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2
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Mutneja A, Karmakar S. Translational dynamics of a rod-like probe in supercooled liquids: an experimentally realizable method to study Stokes-Einstein breakdown, dynamic heterogeneity, and amorphous order. SOFT MATTER 2021; 17:5738-5746. [PMID: 34018543 DOI: 10.1039/d1sm00509j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The use of probe molecules to extract the local dynamical and structural properties of complex dynamical systems is an age-old technique both in simulations and in experiments. A lot of important information which is not immediately accessible from bulk measurements can be accessed via these local measurements. Still, a detailed understanding of how a probe particle dynamics is affected by the surrounding liquid medium is lacking, especially in the supercooled temperature regime. This work shows how the translational dynamics of a rod-like particle immersed in a supercooled liquid can give us information on the growth of the correlation length scales associated with dynamical heterogeneity and the multi-body static correlations in the medium. This work also provides an understanding of the breakdown of Stokes-Einstein and Stokes-Einstein-Debye relations in supercooled liquids along with a unified scaling theory that rationalizes all the observed results. Finally, this work proposes a novel yet simple method accessible in experiments to measure the growth of these important length scales in molecular glass-forming liquids.
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Affiliation(s)
- Anoop Mutneja
- Tata Institute of Fundamental Research, 36/P,Gopanpally Village, Serilingampally Mandal, Ranga Reddy District, Hyderabad, 500107, India.
| | - Smarajit Karmakar
- Tata Institute of Fundamental Research, 36/P,Gopanpally Village, Serilingampally Mandal, Ranga Reddy District, Hyderabad, 500107, India.
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3
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Park H, Park CB, Sung BJ. The effects of vacancies and their mobility on the dynamic heterogeneity in 1,3-dimethylimidazolium hexafluorophosphate organic ionic plastic crystals. Phys Chem Chem Phys 2021; 23:11980-11989. [PMID: 34002734 DOI: 10.1039/d1cp00952d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Organic ionic plastic crystals (OIPCs) are the crystals of electrolytes with a long-range translational order. The rotational modes of ions in OIPCs are, however, activated even in solid phases such that the diffusion of dopants such as lithium ions may be facilitated. OIPCs have been, therefore, considered as good candidates for solid electrolytes. Recent experiments and theoretical studies have suggested that both the translational and the rotational diffusion of ions are quite heterogeneous: the diffusion of some ions are quite fast while other ions of the same kind hardly diffuse, either rotationally or translationally. Such dynamic heterogeneity would be a key to the transport mechanism of dopants in solid state electrolytes. In this work, we investigate the effects of defects on the dynamic heterogeneity of OIPCs. We perform atomistic molecular dynamics simulation of 1,3-dimethylimidazolium hexafluorophosphate ([MMIM][PF6]) with a pair of cation and anion vacancies. At low temperature, vacancies undergo hopping motions toward each other and form a charge-neutral cluster. At high temperature, two vacancies act like a loosely bonded molecule and diffuse together via hopping motions. We find that the translational diffusion of ions is correlated strongly with the vacancy diffusion and becomes heterogeneous when the vacancies hop. The rotation of ions also becomes active when the ions are close to vacancies such that the rotational dynamic heterogeneity strengthens.
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Affiliation(s)
- Hyungshick Park
- Department of Chemistry, Sogang University, Seoul 04107, Republic of Korea.
| | - Chung Bin Park
- Department of Chemistry, Sogang University, Seoul 04107, Republic of Korea.
| | - Bong June Sung
- Department of Chemistry, Sogang University, Seoul 04107, Republic of Korea.
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4
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Cho HW, Shi G, Kirkpatrick TR, Thirumalai D. Random First Order Transition Theory for Glassy Dynamics in a Single Condensed Polymer. PHYSICAL REVIEW LETTERS 2021; 126:137801. [PMID: 33861095 DOI: 10.1103/physrevlett.126.137801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 12/21/2020] [Accepted: 03/01/2021] [Indexed: 06/12/2023]
Abstract
The number of compact structures of a single condensed polymer (SCP), with similar free energies, grows exponentially with the degree of polymerization. In analogy with structural glasses (SGs), we expect that at low temperatures chain relaxation should occur by activated transitions between the compact metastable states. By evolving the states of the SCP, linearly coupled to a reference state, we show that, below a dynamical transition temperature (T_{d}), the SCP is trapped in a metastable state leading to slow dynamics. At a lower temperature, T_{K}≠0, the configurational entropy vanishes, resulting in a thermodynamic random first order ideal glass transition. The relaxation time obeys the Vogel-Fulcher-Tamman law, diverging at T=T_{0}≈T_{K}. These findings, accord well with the random first order transition theory, establishing that SCP and SG exhibit similar universal characteristics.
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Affiliation(s)
- Hyun Woo Cho
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, USA
- Department of Fine Chemistry, Seoul National University of Science and Technology, Seoul 01811, Korea
| | - Guang Shi
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, USA
| | - T R Kirkpatrick
- Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA
| | - D Thirumalai
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, USA
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5
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Kwon S, Sung BJ. History-dependent nonequilibrium conformations of a highly confined polymer globule in a sphere. Phys Rev E 2020; 102:022501. [PMID: 32942375 DOI: 10.1103/physreve.102.022501] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 07/28/2020] [Indexed: 11/07/2022]
Abstract
Chromatin undergoes condensation-decondensation processes repeatedly during its cell lifetime. The spatial organization of chromatin in nucleus resembles the fractal globule, of which structure significantly differs from an equilibrium polymer globule. There have been efforts to develop a polymer globule model to describe the fractal globulelike structure of tightly packed chromatin in nucleus. However, the transition pathway of a polymer toward a globular state has been often ignored. Because biological systems are intrinsically in nonequilibrium states, the transition pathway that the chromatin would take before reaching the densely packaged globule should be of importance. In this study, by employing a simple polymer model and Langevin dynamics simulations, we investigate the conformational transition of a single polymer from a swollen coil to a compact globule. We aim to elucidate the effect of transition pathways on the final globular structure. We show that a fast collapse induces a nonequilibrium structure even without a specific intramolecular interaction and that its relaxation toward an equilibrium globule is extremely slow. Due to a strong confinement, the fractal globule never relaxes into an equilibrium state during our simulations such that the globular structure becomes dependent on the transition pathway.
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Affiliation(s)
- Seulki Kwon
- Department of Chemistry, Sogang University, Seoul 121-742, Republic of Korea
| | - Bong June Sung
- Department of Chemistry, Sogang University, Seoul 121-742, Republic of Korea
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6
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Park CB, Sung BJ. Heterogeneous Rotational Dynamics of Imidazolium-Based Organic Ionic Plastic Crystals. J Phys Chem B 2020; 124:6894-6904. [PMID: 32628857 DOI: 10.1021/acs.jpcb.0c02433] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Organic ionic plastic crystals (OIPCs) are a unique class of materials that undergo orientational and conformational motions while maintaining a long-range ordered lattice structure. OIPCs have attracted attention because the rotational motions were known to accelerate the diffusion of mobile ions such as lithium ions. However, only a small number of combinations of cations and anions lead to OIPCs because the rotational motion may be restricted by both the molecular structure and the crystal class. In this work, we perform molecular dynamics simulations to study the effects of the molecular structure and the crystal class on the rotational motion and the phase transitions. We investigate four imidazolium-based ionic crystals: (1) 1-methyl-3-methylimidazolium hexafluorophosphate ([MMIM][PF6]), (2) 1-methyl-3-methylimidazolium chloride ([MMIM][Cl]), (3) monoclinic 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]), and (4) orthorhombic [BMIM][Cl] ionic crystals. We construct initial configurations of OIPCs by employing experimental crystalline structures. Then, we increase the temperature gradually and monitor the density and the radial distribution functions. We estimate the rotational van Hove correlation functions and find that molecules in plastic crystal phases undergo rotational hopping motions and OIPCs exhibit rotational dynamic heterogeneity significantly. The structure of anions and cations affect the phase transition of OIPCs. And the crystal class is also critical to the phase transition of OIPCs because the rotational motion of ions depends on the crystal class.
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Affiliation(s)
- Chung Bin Park
- Department of Chemistry and Research Institute for Basic Science, Sogang University, Seoul 04107, Republic of Korea
| | - Bong June Sung
- Department of Chemistry and Research Institute for Basic Science, Sogang University, Seoul 04107, Republic of Korea
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Lee YR, Kwon S, Sung BJ. The non-classical kinetics and the mutual information of polymer loop formation. J Chem Phys 2020; 152:184905. [PMID: 32414275 DOI: 10.1063/5.0005453] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The loop formation of a single polymer chain has served as a model system for various biological and chemical processes. Theories based on the Smoluchowski equation proposed that the rate constant (kloop) of the loop formation would be inversely proportional to viscosity (η), i.e., kloop ∼ η-1. Experiments and simulations showed, however, that kloop showed the fractional viscosity dependence of kloop ∼ η-β with β < 1 either in glasses or in low-viscosity solutions. The origin of the fractional viscosity dependence remains elusive and has been attributed to phenomenological aspects. In this paper, we illustrate that the well-known failure of classical kinetics of the loop formation results from the breakdown of the local thermal equilibrium (LTE) approximation and that the mutual information can quantify the breakdown of the LTE successfully.
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Affiliation(s)
- Young-Ro Lee
- Department of Chemistry, Sogang University, Seoul 04107, South Korea
| | - Seulki Kwon
- Department of Chemistry, Sogang University, Seoul 04107, South Korea
| | - Bong June Sung
- Department of Chemistry, Sogang University, Seoul 04107, South Korea
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Mukherjee M, Mondal J, Karmakar S. Role of α and β relaxations in collapsing dynamics of a polymer chain in supercooled glass-forming liquid. J Chem Phys 2019; 150:114503. [PMID: 30901993 DOI: 10.1063/1.5085077] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Understanding the effect of glassy dynamics on the stability of bio-macromolecules and investigating the underlying relaxation processes governing degradation processes of these macromolecules are of immense importance in the context of bio-preservation. In this work, we have studied the stability of a model polymer chain in a supercooled glass-forming liquid at different amounts of supercooling in order to understand how dynamics of supercooled liquids influence the collapse behavior of the polymer. Our systematic computer simulation studies find that, apart from long time relaxation processes (α relaxation), short time dynamics of the supercooled liquid, known as β relaxation, is also correlated with the stability of the model polymer. We also show that anti-plasticizing effect found in this context can be rationalized using the β-relaxation process and how it is modified due to changes in the specific interactions between the biomolecules and the solvent molecules or changes in the local packing around the biomolecules. Our results corroborate with other recent results which suggest that it is important to take in to account both the α and β relaxation times while choosing appropriate bio-preservatives. We believe that our results will have implications in understanding the primary factors in protein stabilization in the context of bio-preservation.
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Affiliation(s)
- Mrinmoy Mukherjee
- Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research, 36/P, Gopanpally Village, Serilingampally Mandal, RR District, Hyderabad 500019, India
| | - Jagannath Mondal
- Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research, 36/P, Gopanpally Village, Serilingampally Mandal, RR District, Hyderabad 500019, India
| | - Smarajit Karmakar
- Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research, 36/P, Gopanpally Village, Serilingampally Mandal, RR District, Hyderabad 500019, India
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Pan D, Sun ZY. Influence of chain stiffness on the dynamical heterogeneity and fragility of polymer melts. J Chem Phys 2018; 149:234904. [DOI: 10.1063/1.5052153] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Deng Pan
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China and University of Chinese Academy of Sciences, Beijing 100039, China
| | - Zhao-Yan Sun
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China and University of Chinese Academy of Sciences, Beijing 100039, China
- Xinjiang Laboratory of Phase Transitions and Microstructures in Condensed Matters, College of Physical Science and Technology, Yili Normal University, Yining 835000, China
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