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David S Corti - One of the best experts on this subject based on the ideXlab platform.
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cavity formation in the superheated lennard jones liquid and its connection to homogeneous Bubble Nucleation a density functional theory study
Journal of Chemical Physics, 2003Co-Authors: Sudeep N Punnathanam, David S CortiAbstract:Recent Monte Carlo simulation studies of a model superheated liquid [Punnathanam and Corti, Ind. Eng. Chem. Res. 41, 1113 (2002)] suggest that cavity formation plays an important role in the process of homogeneous Bubble Nucleation. These simulations revealed that when spherical cavities beyond some certain size, i.e., the so-called critical cavity, were placed inside the superheated Lennard-Jones liquid, an instability was generated that led to phase separation towards the stable vapor phase. In this paper, we explore further the relevance of cavities, and the critical cavity in particular, to the molecular mechanism of homogeneous Bubble Nucleation. Density-functional theory (DFT) calculations are used to verify the existence of the critical cavity within the superheated Lennard-Jones liquid. In addition, DFT reveals that the critical cavity represents a limit of thermodynamic stability, further strengthening the connection between cavities and Bubble Nucleation. The DFT calculations also show that the size of the critical cavity is a lower bound to the size of the critical Bubble and the work of formation of the critical cavity is a tight upper bound to the work of formation of the critical Bubble. These results suggest that the free energy surface of Bubble Nucleation is influenced by the properties of the critical cavity, thereby possibly leading to a new picture of the molecular mechanism of Bubble formation in superheated liquids.
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homogeneous Bubble Nucleation in stretched fluids cavity formation in the superheated lennard jones liquid
Industrial & Engineering Chemistry Research, 2002Co-Authors: Sudeep N Punnathanam, David S CortiAbstract:A consideration of various ideas set forth within the scaled particle theory of hard particle fluids, which are also applicable to systems whose particles interact via attractive potentials, suggests that cavity formation plays an important role in the molecular mechanism of the liquid-to-vapor transition. Umbrella sampling Monte Carlo simulations are used to calculate the reversible work of forming cavities of various sizes within the superheated Lennard-Jones liquid maintained at several negative pressures. A critical cavity size is found to occur, beyond which the liquid would phase separate if not for a density constraint that is applied during the simulation. The work of forming this critically sized cavity and its radius is found to decrease as the liquid approaches the spinodal. A critical cavity size is also found for the superheated liquid at positive pressures. The focus on cavity growth in superheated liquids amounts to a new way of studying Bubble Nucleation and should lead to an improved molecular-based understanding of the kinetics of first-order phase transitions in liquids.
James E Gardner - One of the best experts on this subject based on the ideXlab platform.
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Reconciling Bubble Nucleation in explosive eruptions with geospeedometers
'Springer Science and Business Media LLC', 2021Co-Authors: Sahand Hajimirza, Helge M Gonnermann, James E GardnerAbstract:The authors simulate Bubble Nucleation in silica-rich magma with conditions appropriate for Plinian eruptions. They demonstrate that the gap between decompression rate estimates from Bubble number density and independent geospeedometers can be largely closed if Nucleation is heterogenous facilitated by magnetite crystals and decompression rate is calculated as time-averaged values
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the impact of dissolved fluorine on Bubble Nucleation in hydrous rhyolite melts
Geochimica et Cosmochimica Acta, 2018Co-Authors: James E Gardner, Sahand Hajimirza, James D Webster, Helge M GonnermannAbstract:Abstract Surface tension of hydrous rhyolitic melt is high enough that large degrees of supersaturation are needed to homogeneously nucleate H2O Bubbles during eruptive magma ascent. This study examines whether dissolved fluorine lowers surface tension of hydrous rhyolite, and thus lowers the supersaturation required for Bubble Nucleation. Fluorine was targeted because it, like H2O, changes melt properties and is highly soluble, unlike all other common magmatic volatiles. Rhyolite melts were saturated at Ps = 245 MPa with H2O fluid that contained F, generating rhyolite with 6.7 ± 0.4 wt.% H2O and 1.1–1.3 wt.% F. When these melts were decompressed rapidly to Pf = 149–202 MPa and quenched after 60 s, Bubbles nucleated at supersaturations of ΔP = Ps − Pf ≥52 MPa, and reached Bubble number densities of NB = 1012–13 m−3 at ΔP = 78–101 MPa. In comparison, rhyolite saturated with 6.34 ± 0.09 wt.% H2O, but only 0.25 wt.% F, did not nucleate Bubbles until ΔP ≥ 100–116 MPa, and even then, at significantly lower NB (
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the impact of dissolved co2 on Bubble Nucleation in water poor rhyolite melts
Chemical Geology, 2016Co-Authors: James E Gardner, James D WebsterAbstract:Abstract Volcanic eruptions of H 2 O-poor rhyolite are enigmas, because gas Bubbles are needed to drive eruptions, but experimental evidence suggests that Bubbles cannot nucleate because there is insufficient H 2 O to overcome the free energy associated with the formation of the Bubble–melt interface. In this study, we examine whether CO 2 in the melt can solve that enigma, possibly by nucleating CO 2 -enriched Bubbles that are then used by H 2 O or lowering the surficial free energy. We use experimental decompressions to examine the affect of dissolved CO 2 at conditions both where H 2 O alone can nucleate Bubbles, and where H 2 O activity is too poor to nucleate Bubbles. Experiments using CO 2 -free, hydrated rhyolite melt at 875–900 °C conditions find that Bubbles nucleate when [H 2 O] = 4.34–4.74 wt.%, once H 2 O supersaturates (∆ c , the ratio of the initial H 2 O content to the expected amount at equilibrium at low pressure) by ~ 2–3. Rhyolite melts with less H 2 O do not nucleate Bubbles, even when ∆ c ≫ 3. Equally hydrated rhyolite melt that also contains 500–1000 ppm CO 2 nucleates Bubbles similarly in terms of the critical ∆ c , except that CO 2 -bearing rhyolite must decompress more to reach a given ∆ c . That difference is just a result of the change in H 2 O solubility in the presence CO 2 . It thus appears that Bubble Nucleation in rhyolite melt is dictated by ∆ c , and does not change in the presence of CO 2 . Importantly, molten rhyolite that is too H 2 O poor to nucleate Bubbles will not nucleate them if they are CO 2 rich. The vesiculation of such melts requires that Bubbles nucleate heterogeneously.
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surface tension of hydrous silicate melts constraints on the impact of melt composition
Journal of Volcanology and Geothermal Research, 2013Co-Authors: James E Gardner, Richard A Ketcham, Gordon MooreAbstract:Abstract The first step in magma degassing is the Nucleation of gas Bubbles. The ability of magma to nucleate Bubbles is moderated by its surface tension, which is thought to vary with melt composition, temperature, and H2O content. Numerous experimental studies of Bubble Nucleation in silicate melts have quantified surface tension, but those experiments have been run at different temperatures and used melts with different dissolved H2O contents. The influence of bulk melt composition may thus be masked. In this study, we decompress hydrous silicate melts that range from phono-tephrite to high-silica rhyolite to investigate conditions needed to trigger homogeneous Bubble Nucleation. Importantly, dissolved water contents are very similar amongst the melts, and all were decompressed at 1150–1200 °C, isolating the influence of melt composition on Bubble Nucleation. Despite the 25 wt.% range in SiO2 content, both the total pressure drop and the degree of supersaturation needed to trigger Bubble Nucleation vary a little. Because supersaturation varies little, σ for all melts falls to fall within a relatively narrow range of 0.065 to 0.080 N m− 1. In addition, σ for an even wider range of anhydrous melts is nearly constant, although five times higher. It thus appears that the bulk composition of silicate melt has little impact on σ. It is also known that the variation in σ with temperature is minor, and thus most differences between measured σ values probably result from differences in H2O content.
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surface tension and Bubble Nucleation in phonolite magmas
Geochimica et Cosmochimica Acta, 2012Co-Authors: James E GardnerAbstract:Abstract Explosive Plinian eruptions tap a wide range of magma compositions, including highly alkaline phonolite magma. Such eruptions are driven by volatiles exsolving from those magmas, and so determining how gas Bubbles form is important to understanding those eruptions. Nucleation of Bubbles in silicate melts is dictated strongly by the surface tension (σ) of the melt, and so this study focuses on determining σ for phonolite melts. Cylinders cored from a sodium-rich phonolite were hydrated with 5.37 ± 0.09 wt.% dissolved water at 150 MPa and 1150 °C, and then decompressed at either 1150 °C or 875 °C. Bubbles nucleated at 1150 °C only when pressure dropped below 95 MPa, in number densities of 104–5 cm−3. At 875 °C Bubbles nucleated only when pressure dropped below 53 MPa, in number densities of 104–7 cm−3. Depending on whether the pressure within critical Bubble nuclei equals the saturation pressure or a variable lower pressure, the observed number densities and Nucleation rates imply that surface tension for Na-rich phonolite is 0.061 or 0.068 N m−1 at 875 °C and 0.052 or 0.066 N m−1 at 1150 °C. Importantly, temperature has little or slightly negative impact on σ, in contrast to the thermal impact on σ of rhyolite melts. Regardless of pressure assumption, the inferred surface tensions indicate that Na-rich phonolite can become highly super-saturated with water before Bubbles nucleate, which could cause them to explosively degas and erupt, similar to highly viscous rhyolites.
Sudeep N Punnathanam - One of the best experts on this subject based on the ideXlab platform.
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cavity formation in the superheated lennard jones liquid and its connection to homogeneous Bubble Nucleation a density functional theory study
Journal of Chemical Physics, 2003Co-Authors: Sudeep N Punnathanam, David S CortiAbstract:Recent Monte Carlo simulation studies of a model superheated liquid [Punnathanam and Corti, Ind. Eng. Chem. Res. 41, 1113 (2002)] suggest that cavity formation plays an important role in the process of homogeneous Bubble Nucleation. These simulations revealed that when spherical cavities beyond some certain size, i.e., the so-called critical cavity, were placed inside the superheated Lennard-Jones liquid, an instability was generated that led to phase separation towards the stable vapor phase. In this paper, we explore further the relevance of cavities, and the critical cavity in particular, to the molecular mechanism of homogeneous Bubble Nucleation. Density-functional theory (DFT) calculations are used to verify the existence of the critical cavity within the superheated Lennard-Jones liquid. In addition, DFT reveals that the critical cavity represents a limit of thermodynamic stability, further strengthening the connection between cavities and Bubble Nucleation. The DFT calculations also show that the size of the critical cavity is a lower bound to the size of the critical Bubble and the work of formation of the critical cavity is a tight upper bound to the work of formation of the critical Bubble. These results suggest that the free energy surface of Bubble Nucleation is influenced by the properties of the critical cavity, thereby possibly leading to a new picture of the molecular mechanism of Bubble formation in superheated liquids.
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homogeneous Bubble Nucleation in stretched fluids cavity formation in the superheated lennard jones liquid
Industrial & Engineering Chemistry Research, 2002Co-Authors: Sudeep N Punnathanam, David S CortiAbstract:A consideration of various ideas set forth within the scaled particle theory of hard particle fluids, which are also applicable to systems whose particles interact via attractive potentials, suggests that cavity formation plays an important role in the molecular mechanism of the liquid-to-vapor transition. Umbrella sampling Monte Carlo simulations are used to calculate the reversible work of forming cavities of various sizes within the superheated Lennard-Jones liquid maintained at several negative pressures. A critical cavity size is found to occur, beyond which the liquid would phase separate if not for a density constraint that is applied during the simulation. The work of forming this critically sized cavity and its radius is found to decrease as the liquid approaches the spinodal. A critical cavity size is also found for the superheated liquid at positive pressures. The focus on cavity growth in superheated liquids amounts to a new way of studying Bubble Nucleation and should lead to an improved molecular-based understanding of the kinetics of first-order phase transitions in liquids.
Jene Andrew Golovchenko - One of the best experts on this subject based on the ideXlab platform.
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nanoscale dynamics of joule heating and Bubble Nucleation in a solid state nanopore
Physical Review E, 2016Co-Authors: Edlyn V Levine, Michael M Burns, Jene Andrew GolovchenkoAbstract:We present a mathematical model for Joule heating of an electrolytic solution in a nanopore. The model couples the electrical and thermal dynamics responsible for rapid and extreme superheating of the electrolyte within the nanopore. The model is implemented numerically with a finite element calculation, yielding a time and spatially resolved temperature distribution in the nanopore region. Temperatures near the thermodynamic limit of superheat are predicted to be attained just before the explosive Nucleation of a vapor Bubble is observed experimentally. Knowledge of this temperature distribution enables the evaluation of related phenomena including Bubble Nucleation kinetics, relaxation oscillation, and Bubble dynamics.
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superheating and homogeneous single Bubble Nucleation in a solid state nanopore
Physical Review Letters, 2014Co-Authors: Gaku Nagashima, Edlyn V Levine, David P Hoogerheide, Michael M Burns, Jene Andrew GolovchenkoAbstract:We demonstrate extreme superheating and single Bubble Nucleation in an electrolyte solution within a nanopore in a thin silicon nitride membrane. The high temperatures are achieved by Joule heating from a highly focused ionic current induced to flow through the pore by modest voltage biases. Conductance, Nucleation, and Bubble evolution are monitored electronically and optically. Temperatures near the thermodynamic limit of superheat are achieved just before Bubble Nucleation with the system at atmospheric pressure. Bubble Nucleation is homogeneous and highly reproducible. This nanopore approach more generally suggests broad application to the excitation, detection, and characterization of highly metastable states of matter.
Jie Hou - One of the best experts on this subject based on the ideXlab platform.
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hydrogen Bubble Nucleation by self clustering density functional theory and statistical model studies using tungsten as a model system
Nuclear Fusion, 2018Co-Authors: Xiang-shan Kong, Yu-wei You, Jie Hou, Jingjing Sun, C S Liu, Jun SongAbstract:Low-energy, high-flux hydrogen irradiation is known to induce Bubble formation in tungsten, but its atomistic mechanisms remain little understood. Using first-principles calculations and statistical models, we studied the self-clustering behaviour of hydrogen in tungsten. Unlike previous speculations that the hydrogen self-clusters are energetically unstable owing to the general repulsion between two hydrogen atoms, we found that 2D platelet-like hydrogen self-clusters could form at high hydrogen concentrations. The attractive binding energy of the hydrogen self-cluster becomes larger as the cluster size increases and plateaus at 0.38 eV/H around size of 40. We found that hydrogen atoms would form 2D platelet-like structures along planes. These hydrogen self-clustering behaviours can be quantitatively understood by the competition between long-ranged elastic attraction and local electronic repulsion among hydrogens. Further analysis showed hydrogen self-clusters to be kinetically feasible and thermodynamically stable above a critical hydrogen concentration. Based on this critical hydrogen concentration, we predicted the hydrogen irradiation condition required for the formation of hydrogen self-clusters. Our predictions showed excellent agreement with the experimental results of hydrogen Bubble formation in tungsten exposed to low-energy hydrogen irradiation. Finally, we proposed a possible mechanism for the hydrogen Bubble Nucleation via hydrogen self-clustering. This work provides mechanistic insights and quantitative models towards understanding of plasma-induced hydrogen Bubble formation in plasma-facing tungsten.
