1
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Ingram S, Reischl B, Vesala T, Vehkamäki H. Ruptures of mixed lipid monolayers under tension and supercooling: implications for nanobubbles in plants. NANOSCALE ADVANCES 2024; 6:3775-3784. [PMID: 39050947 PMCID: PMC11265596 DOI: 10.1039/d4na00316k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Accepted: 06/10/2024] [Indexed: 07/27/2024]
Abstract
Mixed phospholipid and glycolipid monolayers likely coat the surfaces of pressurised gas nanobubbles within the hydraulic systems of plants. The lipid coatings bond to water under negative pressure and are thus stretched out of equilibrium. In this work, we have used molecular dynamics simulations to produce trajectories of a biologically relevant mixed monolayer, pulled at mild negative pressures (-1.5 to -4.5 MPa). Pore formation within the monolayer is observed at both 270 and 310 K, and proceeds as an activated process once the lipid tails fully transition from the two dimensional liquid condensed to liquid expanded phase. Pressure:area isotherms showed reduced surface pressure under slight supercooling (T = 270 K) at all observed areas per lipid. Finally, Rayleigh-Plesset simulations were used to predict evolving nanobubble size using the calculated pressure:area isotherms as dynamic surface tensions. We confirm the existence of a second critical radius with respect to runaway growth, above the homogeneous cavitation radius.
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Affiliation(s)
- Stephen Ingram
- Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki P.O. Box 64 Helsinki FI-00014 Finland
| | - Bernhard Reischl
- Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki P.O. Box 64 Helsinki FI-00014 Finland
| | - Timo Vesala
- Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki P.O. Box 64 Helsinki FI-00014 Finland
- Institute for Atmospheric and Earth System Research/Forest Sciences, Faculty of Agriculture and Forestry, University of Helsinki P.O. Box 27 Helsinki FI-00014 Finland
| | - Hanna Vehkamäki
- Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki P.O. Box 64 Helsinki FI-00014 Finland
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2
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Al-Awad AS, Batet L, Rives R, Sedano L. Stochastic computer experiments of the thermodynamic irreversibility of bulk nanobubbles in supersaturated and weak gas-liquid solutions. J Chem Phys 2024; 161:024503. [PMID: 38984961 DOI: 10.1063/5.0204665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2024] [Accepted: 06/24/2024] [Indexed: 07/11/2024] Open
Abstract
Spontaneous gas-bubble nucleation in weak gas-liquid solutions has been a challenging topic in theory, experimentation, and computer simulations. In analogy with recent advances in crystallization and droplet formation studies, the diffusive-shielding stabilization and thermodynamic irreversibility of bulk nanobubble (bNB) mechanisms are revisited and deployed to characterize nucleation processes in a stochastic framework of computer experiments using the large-scale atomic/molecular massively parallel simulator code. Theoretical bases, assumptions, and limitations underlying the irreversibility hypothesis of bNBs, and their computational counterparts, are extensively described and illustrated. In essence, it is established that the irreversibility hypothesis can be numerically investigated by converging the system volume (due to the finiteness of interatomic forces) and the initial dissolved-gas concentration in the solution (due to the single-bNB limitation). Helium nucleation in liquid Pb17Li alloy is selected as a representative case study, where it exhibits typical characteristics of noble-gas/liquid-metal systems. The proposed framework lays down the bases on which the stability of gas-bNBs in weak and supersaturated gas-liquid solutions can be inferred and explained from a novel perspective. In essence, it stochastically marches toward a unique irreversible state along out-of-equilibrium nucleation/growth trajectories. Moreover, it does not attempt to characterize the interface or any interface-related properties, neither theoretically nor computationally. It was concluded that bNBs of a few tens of He-atoms are irreversible when dissolved-He concentrations in the weak gas-liquid solution are at least ∼50 and ∼105 mol m-3 at 600 and 1000 K (and ∼80 MPa), respectively, whereas classical molecular dynamics -estimated solubilities are at least two orders of magnitude smaller.
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Affiliation(s)
- Abdulrahman S Al-Awad
- Department of Physics, Universitat Politècnica de Catalunya-BarcelonaTech (UPC), Barcelona 08028, Spain
| | - Lluis Batet
- Department of Physics, Universitat Politècnica de Catalunya-BarcelonaTech (UPC), Barcelona 08028, Spain
| | - Ronny Rives
- Department of Physics, Universitat Politècnica de Catalunya-BarcelonaTech (UPC), Barcelona 08028, Spain
| | - Luis Sedano
- Department of Physics, Universitat Politècnica de Catalunya-BarcelonaTech (UPC), Barcelona 08028, Spain
- Instituto de Ciencia de Materiales de Barcelona (ICMAB/CSIC), Bellaterra 08193, Spain
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3
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Sanchez-Burgos I, Muniz MC, Espinosa JR, Panagiotopoulos AZ. A Deep Potential model for liquid-vapor equilibrium and cavitation rates of water. J Chem Phys 2023; 158:2889532. [PMID: 37158636 DOI: 10.1063/5.0144500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 03/30/2023] [Indexed: 05/10/2023] Open
Abstract
Computational studies of liquid water and its phase transition into vapor have traditionally been performed using classical water models. Here, we utilize the Deep Potential methodology-a machine learning approach-to study this ubiquitous phase transition, starting from the phase diagram in the liquid-vapor coexistence regime. The machine learning model is trained on ab initio energies and forces based on the SCAN density functional, which has been previously shown to reproduce solid phases and other properties of water. Here, we compute the surface tension, saturation pressure, and enthalpy of vaporization for a range of temperatures spanning from 300 to 600 K and evaluate the Deep Potential model performance against experimental results and the semiempirical TIP4P/2005 classical model. Moreover, by employing the seeding technique, we evaluate the free energy barrier and nucleation rate at negative pressures for the isotherm of 296.4 K. We find that the nucleation rates obtained from the Deep Potential model deviate from those computed for the TIP4P/2005 water model due to an underestimation in the surface tension from the Deep Potential model. From analysis of the seeding simulations, we also evaluate the Tolman length for the Deep Potential water model, which is (0.091 ± 0.008) nm at 296.4 K. Finally, we identify that water molecules display a preferential orientation in the liquid-vapor interface, in which H atoms tend to point toward the vapor phase to maximize the enthalpic gain of interfacial molecules. We find that this behavior is more pronounced for planar interfaces than for the curved interfaces in bubbles. This work represents the first application of Deep Potential models to the study of liquid-vapor coexistence and water cavitation.
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Affiliation(s)
- Ignacio Sanchez-Burgos
- Maxwell Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, J J Thomson Avenue,Cambridge CB3 0HE, United Kingdom
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Maria Carolina Muniz
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Jorge R Espinosa
- Maxwell Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, J J Thomson Avenue,Cambridge CB3 0HE, United Kingdom
- Departamento de Química Fisica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
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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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Ingram S, Salmon Y, Lintunen A, Hölttä T, Vesala T, Vehkamäki H. Dynamic Surface Tension Enhances the Stability of Nanobubbles in Xylem Sap. FRONTIERS IN PLANT SCIENCE 2021; 12:732701. [PMID: 34975934 PMCID: PMC8716698 DOI: 10.3389/fpls.2021.732701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 11/29/2021] [Indexed: 05/28/2023]
Abstract
Air seeded nanobubbles have recently been observed within tree sap under negative pressure. They are stabilized by an as yet unidentified process, although some embolize their vessels in extreme circumstances. Current literature suggests that a varying surface tension helps bubbles survive, but few direct measurements of this quantity have been made. Here, we present calculations of dynamic surface tension for two biologically relevant lipids using molecular dynamics simulations. We find that glycolipid monolayers resist expansion proportionally to the rate of expansion. Their surface tension increases with the tension applied, in a similar way to the viscosity of a non-Newtonian fluid. In contrast, a prototypical phospholipid was equally resistant to all applied tensions, suggesting that the fate of a given nanobubble is dependent on its surface composition. By incorporating our results into a Classical Nucleation Theory (CNT) framework, we predict nanobubble stability with respect to embolism. We find that the metastable radius of glycolipid coated nanobubbles is approximately 35 nm, and that embolism is in this case unlikely when the external pressure is less negative than -1.5 MPa.
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Affiliation(s)
- Stephen Ingram
- Institute for Atmospheric and Earth System Research/Physics, University of Helsinki, Helsinki, Finland
| | - Yann Salmon
- Institute for Atmospheric and Earth System Research/Physics, University of Helsinki, Helsinki, Finland
- Institute for Atmospheric and Earth System Research/Forest Sciences, University of Helsinki, Helsinki, Finland
| | - Anna Lintunen
- Institute for Atmospheric and Earth System Research/Physics, University of Helsinki, Helsinki, Finland
- Institute for Atmospheric and Earth System Research/Forest Sciences, University of Helsinki, Helsinki, Finland
| | - Teemu Hölttä
- Institute for Atmospheric and Earth System Research/Forest Sciences, University of Helsinki, Helsinki, Finland
| | - Timo Vesala
- Institute for Atmospheric and Earth System Research/Physics, University of Helsinki, Helsinki, Finland
- Institute for Atmospheric and Earth System Research/Forest Sciences, University of Helsinki, Helsinki, Finland
- Laboratory of Ecosystem-Atmospheric Interactions of Forest – Mire Complexes, Yugra State University, Khanty-Mansiysk, Russia
| | - Hanna Vehkamäki
- Institute for Atmospheric and Earth System Research/Physics, University of Helsinki, Helsinki, Finland
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6
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Berkowitz ML. Stretch-Induced Cavitation: How Critical Cavity Radius and Barrier Energy, Radius, and Energy of a Stable Cavity Depend on the Stretching Factor. J Phys Chem B 2021; 125:4409-4414. [PMID: 33896169 DOI: 10.1021/acs.jpcb.1c00096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Characteristics of tension-induced cavitation, such as free energy at the barrier for cavitation, the size of the critical (barrier) cavity, the stable cavity size, and the free energy of the stable cavity, depend on the amount of tension (stretch) and the initial size of the sample. In this work, we study how the characteristics of the cavitation mentioned above scale with the amount of applied tension. We consider two models characterizing the properties of cavitating liquid: (a) a simple model with a linear tension-strain relation and neglect of curvature dependence of cavity surface tension and (b) a more realistic model with a nonlinear tension-strain relation and curvature-dependent surface tension. For both models, we find the relevant scaling relations when we stretch the initial volume of the liquid sample in the interval between 1% and 20% of the initial volume. Specific numerical tests are performed for the case of liquid water when the initial volume of the sample is a sphere with a radius of 100 nm.
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Affiliation(s)
- Max L Berkowitz
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
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7
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Min SH, Wijesinghe S, Berkowitz ML. Enhanced Cavitation and Hydration Crossover of Stretched Water in the Presence of C 60. J Phys Chem Lett 2019; 10:6621-6625. [PMID: 31609628 DOI: 10.1021/acs.jpclett.9b02511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We performed molecular dynamics simulations on systems containing stretched water and a C60 buckyball molecule. Our goals were to understand how the presence of the hydrophobic impurity influences the rate of cavitation in stretched water and how the change in pressure (an increase in the value of negative pressure) affects the nature of hydrophobic hydration. Our simulations show that the presence of a buckyball increases the rate of cavitation in water under negative pressure. When studying the influence of the degree of stretching on hydration, we observed that at pressures above -100 MPa the mechanism of hydrophobic hydration is the one that characterizes hydration of a small particle. At some pressure below -100 MPa, there is a crossover in the mechanism of hydration where dewetting occurs by forming cavities next to the surface of the buckyball, and this is characteristic of hydrophobic hydration of large particles.
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Affiliation(s)
- Sa Hoon Min
- Department of Chemistry , The University of North Carolina at Chapel Hill , Chapel Hill , North Carolina 27599 , United States
| | - Sidath Wijesinghe
- Department of Chemistry , The University of North Carolina at Chapel Hill , Chapel Hill , North Carolina 27599 , United States
| | - Max L Berkowitz
- Department of Chemistry , The University of North Carolina at Chapel Hill , Chapel Hill , North Carolina 27599 , United States
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8
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Li B, Gu Y, Chen M. Cavitation inception of water with solid nanoparticles: A molecular dynamics study. ULTRASONICS SONOCHEMISTRY 2019; 51:120-128. [PMID: 30420302 DOI: 10.1016/j.ultsonch.2018.10.036] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2018] [Revised: 10/28/2018] [Accepted: 10/29/2018] [Indexed: 05/24/2023]
Abstract
Cavitation in liquid with impurities is important in heterogeneous nucleation applications. One of the most widely existing kinds of impurities is solid particles, which can be found in natural water from rivers and specially prepared water such as nanofluids. Understanding the effects caused by the existence of nanoparticles on cavitation in water is vital to the rapidly developed nanotechnologies and medical researches. In this study, cavitation in water with nanoparticles is investigated through molecular dynamics simulations. The effects by nanoparticle materials and sizes on cavitation are discussed by using SiO2 and polyethylene spherical nanoparticles with different diameters. The nucleation rate and the formation of critical bubbles in cavitation are studied via the Voronoi tessellation and the mean first passage time methods. The hydrogen bond network in water is also analyzed. Results reveal that SiO2 and polyethylene nanoparticles may destabilize the hydrogen bond network in water. With the same particle size, cavitation in water with polyethylene nanoparticles is promoted to a greater extent than that with SiO2 nanoparticles. With the same nanoparticle material, cavitation is promoted with the increase in particle size in a range spanning half to ten times the critical bubble radius. Beyond this range, particle size has little influence on cavitation. Reasons for those effects on cavitation due to the presence of solid nanoparticles are discussed by analysing the changes of hydrogen bonds network in water.
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Affiliation(s)
- Buxuan Li
- Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
| | - Youwei Gu
- Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
| | - Min Chen
- Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China.
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9
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Min SH, Berkowitz ML. Bubbles in water under stretch-induced cavitation. J Chem Phys 2019; 150:054501. [DOI: 10.1063/1.5079735] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Affiliation(s)
- Sa Hoon Min
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Max L. Berkowitz
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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10
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Elder RM, Long TR, Bain ED, Lenhart JL, Sirk TW. Mechanics and nanovoid nucleation dynamics: effects of polar functionality in glassy polymer networks. SOFT MATTER 2018; 14:8895-8911. [PMID: 30209509 DOI: 10.1039/c8sm01483c] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We use molecular simulations and experiments to rationalize the properties of a class of networks based on dicyclopentadiene (DCPD), a polymer with excellent fracture toughness and a high glass transition temperature (Tg), copolymerized with 5-norbornene-2-methanol (NBOH). DCPD is a highly non-polar hydrocarbon, while NBOH contains a hydroxy group, introducing polar functionality and hydrogen bonds (H-bonds). NBOH thus represents a possible route to improve the chemical compatibility of DCPD-based networks with less-hydrophobic materials. We systematically vary the NBOH content (polar chemistry) in DCPD networks, while keeping other network parameters nearly constant, including the molecular weight between cross-links, chain rigidity, and Tg. Using molecular dynamics (MD) simulations, we quantify the thermovolumetric and mechanical properties, including Tg, cohesive energy density, stiffness, and yield strength. We compare these results with experiments on networks of similar composition, finding good agreement. The relation between these properties and polar chemistry are studied by examining a secondary network of physical cross-links, formed by hydrogen bonds between NBOH units. Further, we examine nanovoid formation, an energy dissipation mechanism hypothesized to contribute to the toughness of pDCPD. Using metadynamics to accelerate sampling, we quantify the nanovoid nucleation rate under hydrostatic tension, similar to the stress state in the plastic zone preceding a crack tip. Small additions of NBOH have minimal effect, but the rate drops steeply with larger amounts. Several properties are mapped at nanometer scales, including stiffness and mobility, and associated with void nucleation. Estimates of the length- and time-scale of the plastic zone near a crack tip are used in discussing nanovoid formation as a plausible toughening mechanism in these materials. Overall, the results suggest that pDCPD tolerates the addition of some polar chemistry without degrading its excellent mechanical properties.
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Affiliation(s)
- Robert M Elder
- Polymers Branch, U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005, USA.
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11
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Langenbach K, Heilig M, Horsch M, Hasse H. Study of homogeneous bubble nucleation in liquid carbon dioxide by a hybrid approach combining molecular dynamics simulation and density gradient theory. J Chem Phys 2018; 148:124702. [DOI: 10.1063/1.5022231] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Affiliation(s)
- K. Langenbach
- Laboratory of Engineering Thermodynamics, University of Kaiserslautern, Kaiserslautern D-67663, Germany
| | - M. Heilig
- ROM, Digitalization in Research and Development, BASF SE, Ludwigshafen D-67056, Germany
| | - M. Horsch
- Laboratory of Engineering Thermodynamics, University of Kaiserslautern, Kaiserslautern D-67663, Germany
| | - H. Hasse
- Laboratory of Engineering Thermodynamics, University of Kaiserslautern, Kaiserslautern D-67663, Germany
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12
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Desgranges C, Delhommelle J. Free energy calculations along entropic pathways. II. Droplet nucleation in binary mixtures. J Chem Phys 2016; 145:234505. [DOI: 10.1063/1.4972011] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Caroline Desgranges
- Department of Chemistry, University of North Dakota, Grand Forks, North Dakota 58202, USA
| | - Jerome Delhommelle
- Department of Chemistry, University of North Dakota, Grand Forks, North Dakota 58202, USA
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13
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Menzl G, Dellago C. Effect of entropy on the nucleation of cavitation bubbles in water under tension. J Chem Phys 2016; 145:211918. [DOI: 10.1063/1.4964327] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Georg Menzl
- Faculty of Physics and Center for Computational Materials Science, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria
| | - Christoph Dellago
- Faculty of Physics and Center for Computational Materials Science, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria
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14
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Desgranges C, Delhommelle J. Free energy calculations along entropic pathways. I. Homogeneous vapor-liquid nucleation for atomic and molecular systems. J Chem Phys 2016; 145:204112. [DOI: 10.1063/1.4968231] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Caroline Desgranges
- Department of Chemistry, University of North Dakota, Grand Forks, North Dakota 58202, USA
| | - Jerome Delhommelle
- Department of Chemistry, University of North Dakota, Grand Forks, North Dakota 58202, USA
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15
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Abstract
Despite its relevance in biology and engineering, the molecular mechanism driving cavitation in water remains unknown. Using computer simulations, we investigate the structure and dynamics of vapor bubbles emerging from metastable water at negative pressures. We find that in the early stages of cavitation, bubbles are irregularly shaped and become more spherical as they grow. Nevertheless, the free energy of bubble formation can be perfectly reproduced in the framework of classical nucleation theory (CNT) if the curvature dependence of the surface tension is taken into account. Comparison of the observed bubble dynamics to the predictions of the macroscopic Rayleigh-Plesset (RP) equation, augmented with thermal fluctuations, demonstrates that the growth of nanoscale bubbles is governed by viscous forces. Combining the dynamical prefactor determined from the RP equation with CNT based on the Kramers formalism yields an analytical expression for the cavitation rate that reproduces the simulation results very well over a wide range of pressures. Furthermore, our theoretical predictions are in excellent agreement with cavitation rates obtained from inclusion experiments. This suggests that homogeneous nucleation is observed in inclusions, whereas only heterogeneous nucleation on impurities or defects occurs in other experiments.
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