1
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Lascaris E, Marchese F, Gaspar N. Crystallization and the liquid-liquid critical point in nonbonded modified-WAC models. J Chem Phys 2024; 161:044503. [PMID: 39037140 DOI: 10.1063/5.0215601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2024] [Accepted: 07/03/2024] [Indexed: 07/23/2024] Open
Abstract
For decades, it has been known that Liquid-Liquid Critical Points (LLCPs) can exist in one-component liquids, yet a comprehensive understanding of the conditions under which they arise remains elusive. To better comprehend the possible interplay between the LLCP and the crystalline phase, we conduct molecular dynamics simulations using the nonbonded family of modified-WAC (mWAC) models, which are known to exhibit a LLCP for certain parameter values. By comparing different versions of the mWAC model-those featuring a LLCP and those lacking one-we identify several key differences between the models relating to crystallization. Those models that do have a LLCP are found to have multiple stable crystalline phases, one of them being a solid-state ionic conductor similar to superionic ice. Moreover, we find that for models that do not have a LLCP, the liquid becomes a glass at a larger range of temperatures, possibly preventing the occurrence of a LLCP. Further studies are required to determine if these results are general or model-specific.
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Affiliation(s)
- Erik Lascaris
- Department of Chemistry & Physical Sciences, Pace University, New York, New York 10038, USA
| | - Francesca Marchese
- Department of Chemistry & Physical Sciences, Pace University, New York, New York 10038, USA
| | - Nicole Gaspar
- Department of Chemistry & Physical Sciences, Pace University, New York, New York 10038, USA
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2
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Chen X, Li Z, Yang C, Yang D. Ionic liquids as the effective technology for enhancing transdermal drug delivery: Design principles, roles, mechanisms, and future challenges. Asian J Pharm Sci 2024; 19:100900. [PMID: 38590797 PMCID: PMC10999516 DOI: 10.1016/j.ajps.2024.100900] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 12/25/2023] [Accepted: 01/08/2024] [Indexed: 04/10/2024] Open
Abstract
Ionic liquids (ILs) have been proven to be an effective technology for enhancing drug transdermal absorption. However, due to the unique structural components of ILs, the design of efficient ILs and elucidation of action mechanisms remain to be explored. In this review, basic design principles of ideal ILs for transdermal drug delivery system (TDDS) are discussed considering melting point, skin permeability, and toxicity, which depend on the molar ratios, types, functional groups of ions and inter-ionic interactions. Secondly, the contributions of ILs to the development of TDDS through different roles are described: as novel skin penetration enhancers for enhancing transdermal absorption of drugs; as novel solvents for improving the solubility of drugs in carriers; as novel active pharmaceutical ingredients (API-ILs) for regulating skin permeability, solubility, release, and pharmacokinetic behaviors of drugs; and as novel polymers for the development of smart medical materials. Moreover, diverse action mechanisms, mainly including the interactions among ILs, drugs, polymers, and skin components, are summarized. Finally, future challenges related to ILs are discussed, including underlying quantitative structure-activity relationships, complex interaction forces between anions, drugs, polymers and skin microenvironment, long-term stability, and in vivo safety issues. In summary, this article will promote the development of TDDS based on ILs.
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Affiliation(s)
- Xuejun Chen
- Department of Pharmacy, Shantou University Medical College, Shantou 515041, China
| | - Ziqing Li
- Department of Pharmacy, Shantou University Medical College, Shantou 515041, China
| | - Chunrong Yang
- Department of Pharmacy, Shantou University Medical College, Shantou 515041, China
| | - Degong Yang
- Department of Pharmacy, Shantou University Medical College, Shantou 515041, China
- Guangdong Provincial Key Laboratory of Infectious Diseases and Molecular Immunopathology, Shantou University Medical College, Shantou 515041, China
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3
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Goswami Y, Sastry S. Kinetic reconstruction of free energies as a function of multiple order parameters. J Chem Phys 2023; 158:144502. [PMID: 37061464 DOI: 10.1063/5.0144338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/17/2023] Open
Abstract
A vast array of phenomena, ranging from chemical reactions to phase transformations, are analyzed in terms of a free energy surface defined with respect to a single or multiple order parameters. Enhanced sampling methods are typically used, especially in the presence of large free energy barriers, to estimate free energies using biasing protocols and sampling of transition paths. Kinetic reconstructions of free energy barriers of intermediate height have been performed, with respect to a single order parameter, employing the steady state properties of unconstrained simulation trajectories when barrier crossing is achievable with reasonable computational effort. Considering such cases, we describe a method to estimate free energy surfaces with respect to multiple order parameters from a steady state ensemble of trajectories. The approach applies to cases where the transition rates between pairs of order parameter values considered is not affected by the presence of an absorbing boundary, whereas the macroscopic fluxes and sampling probabilities are. We demonstrate the applicability of our prescription on different test cases of random walkers executing Brownian motion in order parameter space with an underlying (free) energy landscape and discuss strategies to improve numerical estimates of the fluxes and sampling. We next use this approach to reconstruct the free energy surface for supercooled liquid silicon with respect to the degree of crystallinity and density, from unconstrained molecular dynamics simulations, and obtain results quantitatively consistent with earlier results from umbrella sampling.
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Affiliation(s)
- Yagyik Goswami
- Theoretical Sciences Unit and School of Advanced Materials, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur Campus, Bengaluru 560064, India
| | - Srikanth Sastry
- Theoretical Sciences Unit and School of Advanced Materials, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur Campus, Bengaluru 560064, India
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4
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Singh Y, Santra M, Singh RS. Anomalous Vapor and Ice Nucleation in Water at Negative Pressures: A Classical Density Functional Theory Study. J Phys Chem B 2023; 127:3312-3324. [PMID: 36989467 DOI: 10.1021/acs.jpcb.2c09136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
Abstract
In contrast to the abundance of work on the anomalous behavior of water, the relationship between the water's thermodynamic anomalies and kinetics of phase transition from metastable water is relatively unexplored. In this work, we have employed classical density functional theory to provide a unified and coherent picture of nucleation (both vapor and ice) from metastable water at negative pressure conditions. Our results suggest a peculiar nonmonotonic temperature dependence of vapor-liquid surface tension at temperatures where vapor-liquid coexistence is metastable with respect to the ice phase. The vapor nucleation barrier on isochoric cooling also shows a nonmonotonic temperature dependence. We further report that, for low density isochores, the temperature of the minimum vapor nucleation barrier (TΔΩv/min*) does not coincide with the temperature of maximum density (TMD) where metastability is maximum. The difference between the TΔΩv/min* and the TMD, however, decreases with increasing the density of the isochore. The vapor nucleation barrier along isobars shows an interesting crossover behavior in the vicinity of the Widom line on lowering the temperature. Our results on the ice nucleation suggest an anomalous retracing behavior of the nucleation barrier along isotherms at negative pressures and theoretically validate the recent findings that the reentrant ice(Ih)-liquid coexistence line can induce a drastic change in the kinetics of ice nucleation. Thus, this study establishes a direct connection between the metastable water's thermodynamic anomalies and the (vapor and ice) nucleation kinetics. In addition, this study provides deeper insights into the origin of the isothermal compressibility maximum on isochoric cooling.
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Affiliation(s)
- Yuvraj Singh
- Department of Physics, Indian Institute of Science Education and Research (IISER) Tirupati, Tirupati, Andhra Pradesh 517507, India
| | - Mantu Santra
- School of Chemical and Materials Sciences, Indian Institute of Technology Goa, Ponda, Goa 403401, India
| | - Rakesh S Singh
- Department of Chemistry, Indian Institute of Science Education and Research (IISER) Tirupati, Tirupati, Andhra Pradesh 517507, India
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5
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Goswami Y, Sastry S. Liquid-liquid phase transition in deeply supercooled Stillinger-Weber silicon. PNAS NEXUS 2022; 1:pgac204. [PMID: 36714873 PMCID: PMC9802493 DOI: 10.1093/pnasnexus/pgac204] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 09/20/2022] [Indexed: 04/25/2023]
Abstract
The existence of a phase transition between two distinct liquid phases in single-component network-forming liquids (e.g. water, silica, silicon) has elicited considerable scientific interest. The challenge, both for experiments and simulations, is that the liquid-liquid phase transition (LLPT) occurs under deeply supercooled conditions, where crystallization occurs very rapidly. Thus, early evidence from numerical equation of state studies was challenged with the argument that slow spontaneous crystallization had been misinterpreted as evidence of a second liquid state. Rigorous free-energy calculations have subsequently confirmed the existence of a LLPT in some models of water, and exciting new experimental evidence has since supported these computational results. Similar results have so far not been found for silicon. Here, we present results from free-energy calculations performed for silicon modeled with the classical, empirical Stillinger-Weber-potential. Through a careful study employing state-of-the-art constrained simulation protocols and numerous checks for thermodynamic consistency, we find that there are two distinct metastable liquid states and a phase transition. Our results resolve a long-standing debate concerning the existence of a liquid-liquid transition in supercooled liquid silicon and address key questions regarding the nature of the phase transition and the associated critical point.
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6
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Shumovskyi NA, Longo TJ, Buldyrev SV, Anisimov MA. Modeling fluid polyamorphism through a maximum-valence approach. Phys Rev E 2022; 106:015305. [PMID: 35974620 DOI: 10.1103/physreve.106.015305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Accepted: 06/07/2022] [Indexed: 06/15/2023]
Abstract
We suggest a simple model to describe polyamorphism in single-component fluids using a maximum-valence approach. The model contains three types of interactions: (i) Atoms attract each other by van der Waals forces that generate a liquid-gas transition at low pressures, (ii) atoms may form covalent bonds that induce association, and (iii) atoms with maximal valence attract or repel each other stronger than other atoms, thus generating liquid-liquid separation. As an example, we qualitatively compare this model with the behavior of liquid sulfur and show that condition (iii) generates a liquid-liquid phase transition in addition to the liquid-gas phase transition.
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Affiliation(s)
| | - Thomas J Longo
- Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA
| | - Sergey V Buldyrev
- Department of Physics, Yeshiva University, New York, New York 10033, USA and Department of Physics, Boston University, Massachusetts 02215, USA
| | - Mikhail A Anisimov
- Department of Chemical and Biomolecular Engineering and Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA
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7
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Martelli F, Palmer JC. Signatures of sluggish dynamics and local structural ordering during ice nucleation. J Chem Phys 2022; 156:114502. [DOI: 10.1063/5.0083638] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We investigate the microscopic pathway of spontaneous crystallization in the ST2 model of water under deeply supercooled conditions via unbiased classical molecular dynamics simulations. After quenching below the liquid–liquid critical point, the ST2 model spontaneously separates into low-density liquid (LDL) and high-density liquid phases, respectively. The LDL phase, which is characterized by lower molecular mobility and enhanced structural order, fosters the formation of a sub-critical ice nucleus that, after a stabilization time, develops into the critical nucleus and grows. Polymorphic selection coincides with the development of the sub-critical nucleus and favors the formation of cubic (Ic) over hexagonal (Ih) ice. We rationalize polymorphic selection in terms of geometric arguments based on differences in the symmetry of second neighbor shells of ice Ic and Ih, which are posited to favor formation of the former. The rapidly growing critical nucleus absorbs both Ic and Ih crystallites dispersed in the liquid phase, a crystal with stacking faults. Our results are consistent with, and expand upon, recent observations of non-classical nucleation pathways in several systems.
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Affiliation(s)
- Fausto Martelli
- IBM Research Europe, Hartree Centre, Daresbury WA4 4AD, United Kingdom
| | - Jeremy C. Palmer
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, USA
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8
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Bhaumik H, Foffi G, Sastry S. Avalanches, Clusters, and Structural Change in Cyclically Sheared Silica Glass. PHYSICAL REVIEW LETTERS 2022; 128:098001. [PMID: 35302798 DOI: 10.1103/physrevlett.128.098001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 01/14/2022] [Accepted: 02/09/2022] [Indexed: 06/14/2023]
Abstract
We investigate avalanches and clusters associated with plastic rearrangements and the nature of structural change in the prototypical strong glass, silica, computationally. We perform a detailed analysis of avalanches, and of spatially disconnected clusters that constitute them, for a wide range of system sizes. Although qualitative aspects of yielding in silica are similar to other glasses, the statistics of clusters exhibits significant differences, which we associate with differences in local structure. Across the yielding transition, anomalous structural change and densification, associated with a suppression of tetrahedral order, is observed to accompany strain localization.
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Affiliation(s)
- Himangsu Bhaumik
- Jawaharlal Nehru Center for Advanced Scientific Research, Jakkur Campus, Bengaluru 560064, India
| | - Giuseppe Foffi
- Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay, France
| | - Srikanth Sastry
- Jawaharlal Nehru Center for Advanced Scientific Research, Jakkur Campus, Bengaluru 560064, India
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9
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Bhaumik H, Foffi G, Sastry S. The role of annealing in determining the yielding behavior of glasses under cyclic shear deformation. Proc Natl Acad Sci U S A 2021; 118:e2100227118. [PMID: 33850022 PMCID: PMC8072236 DOI: 10.1073/pnas.2100227118] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Yielding behavior in amorphous solids has been investigated in computer simulations using uniform and cyclic shear deformation. Recent results characterize yielding as a discontinuous transition, with the degree of annealing of glasses being a significant parameter. Under uniform shear, discontinuous changes in stresses at yielding occur in the high annealing regime, separated from the poor annealing regime in which yielding is gradual. In cyclic shear simulations, relatively poorly annealed glasses become progressively better annealed as the yielding point is approached, with a relatively modest but clear discontinuous change at yielding. To understand better the role of annealing on yielding characteristics, we perform athermal quasistatic cyclic shear simulations of glasses prepared with a wide range of annealing in two qualitatively different systems-a model of silica (a network glass) and an atomic binary mixture glass. Two strikingly different regimes of behavior emerge. Energies of poorly annealed samples evolve toward a unique threshold energy as the strain amplitude increases, before yielding takes place. Well-annealed samples, in contrast, show no significant energy change with strain amplitude until they yield, accompanied by discontinuous energy changes that increase with the degree of annealing. Significantly, the threshold energy for both systems corresponds to dynamical cross-over temperatures associated with changes in the character of the energy landscape sampled by glass-forming liquids.
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Affiliation(s)
- Himangsu Bhaumik
- Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bengaluru 560064, India
| | - Giuseppe Foffi
- Laboratoire de Physique des Solides, Université Paris-Saclay, CNRS, 91405 Orsay, France
| | - Srikanth Sastry
- Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bengaluru 560064, India;
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10
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Horstmann R, Vogel M. Relations between thermodynamics, structures, and dynamics for modified water models in their supercooled regimes. J Chem Phys 2021; 154:054502. [DOI: 10.1063/5.0037080] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Affiliation(s)
- R. Horstmann
- Institute of Condensed Matter Physics, Technische Universität Darmstadt, Hochschulstr. 6, 64289 Darmstadt, Germany
| | - M. Vogel
- Institute of Condensed Matter Physics, Technische Universität Darmstadt, Hochschulstr. 6, 64289 Darmstadt, Germany
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11
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Affiliation(s)
- Hajime Tanaka
- Department of Fundamental Engineering, Institute of Industrial Science, University of Tokyo, Meguro-ku, Tokyo 153-8505, Japan
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12
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Wang M, Falke S, Schubert R, Lorenzen K, Cheng QD, Exner C, Brognaro H, Mudogo CN, Betzel C. Pulsed electric fields induce modulation of protein liquid-liquid phase separation. SOFT MATTER 2020; 16:8547-8553. [PMID: 32909579 DOI: 10.1039/d0sm01478h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The time-resolved dynamic assembly and the structures of protein liquid dense clusters (LDCs) were analyzed under pulsed electric fields (EFs) applying complementary polarized and depolarized dynamic light scattering (DLS/DDLS), optical microscopy, and transmission electron microscopy (TEM). We discovered that pulsed EFs substantially affected overall morphologies and spatial distributions of protein LDCs and microcrystals, and affected the phase diagrams of LDC formation, including enabling protein solutions to overcome the diffusive flux energy barrier to phase separate. Data obtained from DLS/DDLS and TEM showed that LDCs appeared as precursors of protein crystal nuclei, followed by the formation of ordered structures within LDCs applying a pulsed EF. Experimental results of circular dichroism spectroscopy provided evidence that the protein secondary structure content is changing under EFs, which may consequently modulate protein-protein interactions, and the morphology, dimensions, and internal structure of LDCs. Data and results obtained unveil options to modulate the phase diagram of crystallization, and physical morphologies of protein LDCs and microcrystals by irradiating sample suspensions with pulsed EFs.
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Affiliation(s)
- Mengying Wang
- Institute of Biochemistry and Molecular Biology, Laboratory for Structural Biology of Infection and Inflammation, c/o DESY, Build. 22a, Notkestr. 85, 22607, Hamburg, Germany.
| | - Sven Falke
- Institute of Biochemistry and Molecular Biology, Laboratory for Structural Biology of Infection and Inflammation, c/o DESY, Build. 22a, Notkestr. 85, 22607, Hamburg, Germany.
| | - Robin Schubert
- European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld, Germany
| | | | - Qing-di Cheng
- Institute of Biochemistry and Molecular Biology, Laboratory for Structural Biology of Infection and Inflammation, c/o DESY, Build. 22a, Notkestr. 85, 22607, Hamburg, Germany.
| | - Christian Exner
- Institute of Biochemistry and Molecular Biology, Laboratory for Structural Biology of Infection and Inflammation, c/o DESY, Build. 22a, Notkestr. 85, 22607, Hamburg, Germany.
| | - Hévila Brognaro
- Institute of Biochemistry and Molecular Biology, Laboratory for Structural Biology of Infection and Inflammation, c/o DESY, Build. 22a, Notkestr. 85, 22607, Hamburg, Germany.
| | - Célestin Nzanzu Mudogo
- Department of Basic Sciences, School of Medicine, University of Kinshasa, Kinshasa, Democratic Republic of Congo
| | - Christian Betzel
- Institute of Biochemistry and Molecular Biology, Laboratory for Structural Biology of Infection and Inflammation, c/o DESY, Build. 22a, Notkestr. 85, 22607, Hamburg, Germany.
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13
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Singh RS, Palmer JC, Panagiotopoulos AZ, Debenedetti PG. Thermodynamic analysis of the stability of planar interfaces between coexisting phases and its application to supercooled water. J Chem Phys 2019; 150:224503. [DOI: 10.1063/1.5097591] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Rakesh S. Singh
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Jeremy C. Palmer
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, USA
| | | | - Pablo G. Debenedetti
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
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14
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Uralcan B, Latinwo F, Debenedetti PG, Anisimov MA. Pattern of property extrema in supercooled and stretched water models and a new correlation for predicting the stability limit of the liquid state. J Chem Phys 2019; 150:064503. [DOI: 10.1063/1.5078446] [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)
- Betul Uralcan
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Folarin Latinwo
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Pablo G. Debenedetti
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Mikhail A. Anisimov
- Department of Chemical and Biomolecular Engineering and Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA
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15
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Palmer JC, Poole PH, Sciortino F, Debenedetti PG. Advances in Computational Studies of the Liquid–Liquid Transition in Water and Water-Like Models. Chem Rev 2018; 118:9129-9151. [DOI: 10.1021/acs.chemrev.8b00228] [Citation(s) in RCA: 116] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jeremy C. Palmer
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Peter H. Poole
- Department of Physics, St. Francis Xavier University, Antigonish, NS B2G 2W5, Canada
| | - Francesco Sciortino
- Dipartimento di Fisica and CNR-ISC, Sapienza Universita’ di Roma, Piazzale A. Moro 5, 00185 Rome, Italy
| | - Pablo G. Debenedetti
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
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16
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Pafong Sanjon E, Drossel B, Vogel M. Effects of the bond polarity on the structural and dynamical properties of silica-like liquids. J Chem Phys 2018; 148:104506. [PMID: 29544292 DOI: 10.1063/1.5017681] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Silica is a network-forming liquid that shares many properties with water due to its tetrahedral structure. It undergoes a transition from a fragile to a strong liquid as the temperature is decreased, which is accompanied by a structural change to lower density and higher tetrahedral order. In order to disentangle the effects of Coulomb and van der Waals interactions on the structure and dynamics of liquid silica, we modify the bond polarity by changing the partial charges assigned to each atom. Using molecular dynamics simulations, we show that density, tetrahedral order, and structural relaxation times decrease when reducing bond polarity. Moreover, we find that the density maximum and the fragile-to-strong transition move to lower temperatures until they eventually vanish when the partial charges are decreased below approximately 75% of their regular value. Irrespective of whether strong or fragile behavior exists, structural relaxation is governed by hopping motion at sufficiently low temperatures. As long as there is a strong regime, the energy barrier associated with strong dynamics decreases with decreasing partial charges, but the dependence on the bond polarity differs from that of the activation energy in the Arrhenius regime at high temperatures. We show that the fragile-to-strong transition is associated with structural changes occurring between the first and second coordination shells that lead to a decrease in density and an increase in tetrahedral order. In particular, independent of the value of the partial charges, the distribution of the local structures is the same at this dynamic crossover, but we find no evidence that the effect occurs upon crossing the Widom line. In the fragile regime at intermediate temperatures, the relaxation times are well described by a previously proposed model which decomposes the apparent activation energy into a constant single-particle contribution and a temperature-dependent collective contribution. However, our results for silica-like melts do not obey several common relations of the model parameters reported for molecular glass formers.
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Affiliation(s)
- E Pafong Sanjon
- Institut für Festkörperphysik, Technische Universität Darmstadt, Hochschulstr. 6, 64289 Darmstadt, Germany
| | - B Drossel
- Institut für Festkörperphysik, Technische Universität Darmstadt, Hochschulstr. 6, 64289 Darmstadt, Germany
| | - M Vogel
- Institut für Festkörperphysik, Technische Universität Darmstadt, Hochschulstr. 6, 64289 Darmstadt, Germany
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17
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Zhao G, Wang H, Hu DM, Ding MC, Zhao XG, Yan JL. Anomalous phase behavior of first-order fluid-liquid phase transition in phosphorus. J Chem Phys 2018; 147:204501. [PMID: 29195280 DOI: 10.1063/1.4999009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Although the existence of liquid-liquid phase transition has become more and more convincing, whether it will terminate at a critical point and what is the order parameter are still open. To explore these questions, we revisit the fluid-liquid phase transition (FLPT) in phosphorus (P) and study its phase behavior by performing extensive first-principles molecular dynamics simulations. The FLPT observed in experiments is well reproduced, and a fluid-liquid critical point (FLCP) at T = 3000 ∼ 3500 K, P = 1.5-2.0 Kbar is found. With decreasing temperature from the FLCP along the transition line, the density difference (Δρ) between two coexisting phases first increases from zero and then anomalously decreases; however, the entropy difference (ΔS) continuously increases from zero. These features suggest that an order parameter containing contributions from both the density and the entropy is needed to describe the FLPT in P, and at least at low temperatures, the entropy, instead of the density, governs the FLPT.
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Affiliation(s)
- G Zhao
- School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, People's Republic of China
| | - H Wang
- School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, People's Republic of China
| | - D M Hu
- School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, People's Republic of China
| | - M C Ding
- School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, People's Republic of China
| | - X G Zhao
- School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, People's Republic of China
| | - J L Yan
- School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, People's Republic of China
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18
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Affiliation(s)
- Jingxiang Guo
- Department of Chemical and Biomolecular Engineering, University of Houston , Houston, TX, USA
| | - Rakesh S. Singh
- Department of Chemistry, Johns Hopkins University , Baltimore, MD, USA
| | - Jeremy C. Palmer
- Department of Chemical and Biomolecular Engineering, University of Houston , Houston, TX, USA
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19
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Higuchi S, Kato D, Awaji D, Kim K. Connecting thermodynamic and dynamical anomalies of water-like liquid-liquid phase transition in the Fermi–Jagla model. J Chem Phys 2018. [DOI: 10.1063/1.5017105] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Saki Higuchi
- Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan
| | - Daiki Kato
- Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan
| | - Daisuke Awaji
- Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan
| | - Kang Kim
- Division of Chemical Engineering, Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
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20
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Guo J, Palmer JC. Fluctuations near the liquid–liquid transition in a model of silica. Phys Chem Chem Phys 2018; 20:25195-25202. [DOI: 10.1039/c8cp04237c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Molecular dynamics simulations reveal anomalous small-angle scattering and liquid–liquid phase separation in an ionic model of silica.
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Affiliation(s)
- Jingxiang Guo
- Department of Chemical and Biomolecular Engineering
- University of Houston
- Houston
- USA
| | - Jeremy C. Palmer
- Department of Chemical and Biomolecular Engineering
- University of Houston
- Houston
- USA
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21
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Wang Z, Li T, Duan Y, Wu W, Zhao Z, Liu Y, Li H. Abnormal separation of the silicon–oxygen bond in the liquid layering transition of silicon dioxide in a nanoslit. Phys Chem Chem Phys 2018; 20:3724-3734. [DOI: 10.1039/c7cp06843c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Layering transition and separation of silicon and oxygen in liquid SiO2 become obvious due to the strengthening of the nanoconfined effect.
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Affiliation(s)
- Zhichao Wang
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials
- Ministry of Education, Shandong University
- Jinan 250061
- People's Republic of China
| | - Tao Li
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials
- Ministry of Education, Shandong University
- Jinan 250061
- People's Republic of China
| | - Yunrui Duan
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials
- Ministry of Education, Shandong University
- Jinan 250061
- People's Republic of China
| | - Weikang Wu
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials
- Ministry of Education, Shandong University
- Jinan 250061
- People's Republic of China
| | - Zhenyang Zhao
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials
- Ministry of Education, Shandong University
- Jinan 250061
- People's Republic of China
| | - Yao Liu
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials
- Ministry of Education, Shandong University
- Jinan 250061
- People's Republic of China
| | - Hui Li
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials
- Ministry of Education, Shandong University
- Jinan 250061
- People's Republic of China
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