scholarly journals Ice-Crystal Nucleation in Water: Thermodynamic Driving Force and Surface Tension. Part I: Theoretical Foundation

Entropy ◽  
2019 ◽  
Vol 22 (1) ◽  
pp. 50 ◽  
Author(s):  
Olaf Hellmuth ◽  
Jürn W. P. Schmelzer ◽  
Rainer Feistel
Keyword(s):  
Surface Tension ◽  
Driving Force ◽  
Mass Density ◽  
Stable State ◽  
Water System ◽  
Ice Nucleation ◽  
Crystal Nucleation ◽  
Temperature And Pressure ◽  
Homogeneous Freezing ◽  
Ice Water

A recently developed thermodynamic theory for the determination of the driving force of crystallization and the crystal–melt surface tension is applied to the ice-water system employing the new Thermodynamic Equation of Seawater TEOS-10. The deviations of approximative formulations of the driving force and the surface tension from the exact reference properties are quantified, showing that the proposed simplifications are applicable for low to moderate undercooling and pressure differences to the respective equilibrium state of water. The TEOS-10-based predictions of the ice crystallization rate revealed pressure-induced deceleration of ice nucleation with an increasing pressure, and acceleration of ice nucleation by pressure decrease. This result is in, at least, qualitative agreement with laboratory experiments and computer simulations. Both the temperature and pressure dependencies of the ice-water surface tension were found to be in line with the le Chatelier–Braun principle, in that the surface tension decreases upon increasing degree of metastability of water (by decreasing temperature and pressure), which favors nucleation to move the system back to a stable state. The reason for this behavior is discussed. Finally, the Kauzmann temperature of the ice-water system was found to amount T K = 116 K , which is far below the temperature of homogeneous freezing. The Kauzmann pressure was found to amount to p K = − 212 MPa , suggesting favor of homogeneous freezing on exerting a negative pressure on the liquid. In terms of thermodynamic properties entering the theory, the reason for the negative Kauzmann pressure is the higher mass density of water in comparison to ice at the melting point.

scholarly journals Ice-Crystal Nucleation in Water: Thermodynamic Driving Force and Surface Tension

2019 ◽  
Author(s):  
Olaf Hellmuth ◽  
Juern W. P. Schmelzer ◽  
Rainer Feistel
Keyword(s):  
Surface Tension ◽  
Driving Force ◽  
Mass Density ◽  
Stable State ◽  
Water System ◽  
Crystallization Rate ◽  
Ice Nucleation ◽  
Crystal Nucleation ◽  
Temperature And Pressure ◽  
Homogeneous Freezing

A recently developed thermodynamic theory for the determination of the driving force of crystallization and the crystal–melt surface tension is applied to the ice–water system employing the new Thermodynamic Equation of Seawater TEOS-10. The deviations of approximative formulations of the driving force and the surface tension from the exact reference properties are quantified, showing that the proposed simplifications are applicable for low to moderate undercooling and pressure differences to the respective equilibrium state of water. The TEOS-10 based predictions of the ice crystallization rate revealed pressure-induced deceleration of ice nucleation with an increasing pressure, and acceleration of ice nucleation by pressure decrease. This result is in, at least, qualitative agreement with laboratory experiments and computer simulations. Both the temperature and pressure dependencies of the ice–water surface tension were found to be in line with the le Chatelier–Braun principle, in that the surface tension decreases upon increasing degree of metastability of water (by decreasing temperature and pressure), which favors nucleation to move the system back to a stable state. The reason for this behavior is discussed. Finally, the Kauzmann temperature of the ice–water system was found to amount TK=116K, which is far below the temperature of homogeneous freezing. The Kauzmann pressure was found to amount pK=-212MPa, suggesting favor of homogeneous freezing upon exerting a negative pressure on the liquid. In terms of thermodynamic properties entering the theory, the reason for the negative Kauzmann pressure is the higher mass density of water in comparison to ice at the melting point.

scholarly journals Effects of Glass Transition and Structural Relaxation on Crystal Nucleation: Theoretical Description and Model Analysis

Entropy ◽  
2020 ◽  
Vol 22 (10) ◽  
pp. 1098 ◽  
Author(s):  
Jürn W. P. Schmelzer ◽  
Timur V. Tropin ◽  
Vladimir M. Fokin ◽  
Alexander S. Abyzov ◽  
Edgar D. Zanotto
Keyword(s):  
Surface Tension ◽  
Structural Relaxation ◽  
Driving Force ◽  
Cluster Formation ◽  
Supercooled Liquid ◽  
Crystal Nucleation ◽  
Metastable Equilibrium ◽  
Theoretical Treatment ◽  
Relaxation Processes ◽  
Thermodynamic Driving Force

In the application of classical nucleation theory (CNT) and all other theoretical models of crystallization of liquids and glasses it is always assumed that nucleation proceeds only after the supercooled liquid or the glass have completed structural relaxation processes towards the metastable equilibrium state. Only employing such an assumption, the thermodynamic driving force of crystallization and the surface tension can be determined in the way it is commonly performed. The present paper is devoted to the theoretical treatment of a different situation, when nucleation proceeds concomitantly with structural relaxation. To treat the nucleation kinetics theoretically for such cases, we need adequate expressions for the thermodynamic driving force and the surface tension accounting for the contributions caused by the deviation of the supercooled liquid from metastable equilibrium. In the present paper, such relations are derived. They are expressed via deviations of structural order parameters from their equilibrium values. Relaxation processes result in changes of the structural order parameters with time. As a consequence, the thermodynamic driving force and surface tension, and basic characteristics of crystal nucleation, such as the work of critical cluster formation and the steady-state nucleation rate, also become time-dependent. We show that this scenario may be realized in the vicinity and below the glass transition temperature, and it may occur only if diffusion (controlling nucleation) and viscosity (controlling the alpha-relaxation process) in the liquid decouple. Analytical estimates are illustrated and confirmed by numerical computations for a model system. The theory is successfully applied to the interpretation of experimental data. Several further consequences of this newly developed theoretical treatment are discussed in detail. In line with our previous investigations, we reconfirm that only when the characteristic times of structural relaxation are of similar order of magnitude or longer than the characteristic times of crystal nucleation, elastic stresses evolving in nucleation may significantly affect this process. Advancing the methods of theoretical analysis of elastic stress effects on nucleation, for the first time expressions are derived for the dependence of the surface tension of critical crystallites on elastic stresses. As the result, a comprehensive theoretical description of crystal nucleation accounting appropriately for the effects of deviations of the liquid from the metastable states and of relaxation on crystal nucleation of glass-forming liquids, including the effect of simultaneous stress evolution and stress relaxation on nucleation, is now available. As one of its applications, this theoretical treatment provides a new tool for the explanation of the low-temperature anomaly in nucleation in silicate and polymer glasses (the so-called “breakdown” of CNT at temperatures below the temperature of the maximum steady-state nucleation rate). We show that this anomaly results from much more complex features of crystal nucleation in glasses caused by deviations from metastable equilibrium (resulting in changes of the thermodynamic driving force, the surface tension, and the work of critical cluster formation, in the necessity to account of structural relaxation and stress effects) than assumed so far. If these effects are properly accounted for, then CNT appropriately describes both the initial, the intermediate, and the final states of crystal nucleation.

scholarly journals Effects of Glass Transition and Structural Relaxation on Crystal Nucleation: Theoretical Description and Model Analysis

2020 ◽  
Author(s):  
Juern W. P. Schmelzer ◽  
Timur V. Tropin ◽  
Vladimir M. Fokin ◽  
Alexander S. Abyzov ◽  
Edgar D. Zanotto
Keyword(s):  
Surface Tension ◽  
Structural Relaxation ◽  
Driving Force ◽  
Cluster Formation ◽  
Supercooled Liquid ◽  
Crystal Nucleation ◽  
Metastable Equilibrium ◽  
Theoretical Treatment ◽  
Relaxation Processes ◽  
Thermodynamic Driving Force

In the application of classical nucleation theory (CNT) and all other theoretical models of crystallization of liquids and glasses it is always assumed that nucleation proceeds only after the supercooled liquid or the glass have completed structural relaxation processes towards the metastable equilibrium state. Only employing such assumption, the thermodynamic driving force of crystallization and the surface tension can be determined in the way it is commonly performed. The present paper is devoted to the theoretical treatment of a different situation when nucleation proceeds concomitantly with structural relaxation. To treat the nucleation kinetics theoretically for such cases, we need adequate expressions for the thermodynamic driving force and the surface tension accounting for the contributions caused by the deviation of the supercooled liquid from metastable equilibrium. In the present paper, such relations are derived. They are expressed via deviations of structural order parameters from their equilibrium values. Relaxation processes result in changes of the structural order parameters with time. As a consequence, the thermodynamic driving force and surface tension, and basic characteristics of crystal nucleation, such as the work of critical cluster formation and the steady-state nucleation rate, also become time-dependent. We show that this scenario may be realized in the vicinity and below the glass transition temperature, and it may occur only if diffusion (controlling nucleation) and viscosity (controlling the alpha-relaxation process) in the liquid decouple. Analytical estimates are illustrated and confirmed by numerical computations for a model system. The theory is successfully applied to the interpretation of experimental data. Several further consequences of this newly developed theoretical treatment are discussed in detail. In line with our previous investigations, we reconfirm that only when the characteristic times of structural relaxation are of similar order of magnitude or longer than the characteristic times of crystal nucleation, elastic stresses evolving in nucleation may significantly affect this process. Completing the analysis of elastic stress effects, for the first time expressions are derived for the dependence of the surface tension of critical crystallites on elastic stresses. As the result, a comprehensive theoretical description of crystal nucleation accounting appropriately for the effects of deviations of the liquid from the metastable states and of relaxation on crystal nucleation of glass-forming liquids, including the effect of simultaneous stress evolution and stress relaxation on nucleation, is now available. As one if its applications, this theoretical treatment provides a new tool for the explanation of the low-temperature anomaly in nucleation in silicate and polymer glasses (the so-called \breakdown" of CNT at temperatures below the temperature of the maximum steady-state nucleation rate). We show that this anomaly results from much more complex features of crystal nucleation in glasses caused by deviations from metastable equilibrium (resulting in changes of the thermodynamic driving force, the surface tension, and the work of critical cluster formation, in the necessity to account of structural relaxation and stress effects) than assumed so far.

The nucleation of cavities at grain boundaries

1987 ◽  
Vol 45 ◽  
pp. 288-291
Author(s):  
P. J. Goodhew
Keyword(s):  
Surface Tension ◽  
Surface Energy ◽  
Grain Boundaries ◽  
Radiation Damage ◽  
Impurity Concentration ◽  
Driving Force ◽  
Nucleation And Growth ◽  
Phase Boundaries ◽  
Cavity Nucleation ◽  
Spherical Bubble

Cavity nucleation and growth at grain and phase boundaries is of concern because it can lead to failure during creep and can lead to embrittlement as a result of radiation damage. Two major types of cavity are usually distinguished: The term bubble is applied to a cavity which contains gas at a pressure which is at least sufficient to support the surface tension (2g/r for a spherical bubble of radius r and surface energy g). The term void is generally applied to any cavity which contains less gas than this, but is not necessarily empty of gas. A void would therefore tend to shrink in the absence of any imposed driving force for growth, whereas a bubble would be stable or would tend to grow. It is widely considered that cavity nucleation always requires the presence of one or more gas atoms. However since it is extremely difficult to prepare experimental materials with a gas impurity concentration lower than their eventual cavity concentration there is little to be gained by debating this point.

Ice-Phase Precipitation

2017 ◽  
Vol 58 ◽  
pp. 6.1-6.36 ◽  
Author(s):  
I. Gultepe ◽  
A. J. Heymsfield ◽  
P. R. Field ◽  
D. Axisa
Keyword(s):  
Collection Efficiency ◽  
Numerical Models ◽  
Mass Density ◽  
Three Dimensional ◽  
Phase Precipitation ◽  
Microphysical Parameters ◽  
Mass Size ◽  
Ice Water ◽  
Ice Phase

AbstractIce-phase precipitation occurs at Earth’s surface and may include various types of pristine crystals, rimed crystals, freezing droplets, secondary crystals, aggregates, graupel, hail, or combinations of any of these. Formation of ice-phase precipitation is directly related to environmental and cloud meteorological parameters that include available moisture, temperature, and three-dimensional wind speed and turbulence, as well as processes related to nucleation, cooling rate, and microphysics. Cloud microphysical parameters in the numerical models are resolved based on various processes such as nucleation, mixing, collision and coalescence, accretion, riming, secondary ice particle generation, turbulence, and cooling processes. These processes are usually parameterized based on assumed particle size distributions and ice crystal microphysical parameters such as mass, size, and number and mass density. Microphysical algorithms in the numerical models are developed based on their need for applications. Observations of ice-phase precipitation are performed using in situ and remote sensing platforms, including radars and satellite-based systems. Because of the low density of snow particles with small ice water content, their measurements and predictions at the surface can include large uncertainties. Wind and turbulence affecting collection efficiency of the sensors, calibration issues, and sensitivity of ground-based in situ observations of snow are important challenges to assessing the snow precipitation. This chapter’s goals are to provide an overview for accurately measuring and predicting ice-phase precipitation. The processes within and below cloud that affect falling snow, as well as the known sources of error that affect understanding and prediction of these processes, are discussed.

scholarly journals Condensed-phase biogenic–anthropogenic interactions with implications for cold cloud formation

2017 ◽  
Vol 200 ◽  
pp. 165-194 ◽  
Author(s):  
Joseph C. Charnawskas ◽  
Peter A. Alpert ◽  
Andrew T. Lambe ◽  
Thomas Berkemeier ◽  
Rachel E. O’Brien ◽  
...  
Keyword(s):  
Freezing Temperature ◽  
Organic Aerosol ◽  
Ice Nucleation ◽  
Mixed Phase ◽  
Cloud Formation ◽  
Fossil Fuel Combustion ◽  
Soot Particles ◽  
Ice Nuclei ◽  
Deliquescence Relative Humidity ◽  
Homogeneous Freezing

Anthropogenic and biogenic gas emissions contribute to the formation of secondary organic aerosol (SOA). When present, soot particles from fossil fuel combustion can acquire a coating of SOA. We investigate SOA–soot biogenic–anthropogenic interactions and their impact on ice nucleation in relation to the particles’ organic phase state. SOA particles were generated from the OH oxidation of naphthalene, α-pinene, longifolene, or isoprene, with or without the presence of sulfate or soot particles. Corresponding particle glass transition (Tg) and full deliquescence relative humidity (FDRH) were estimated using a numerical diffusion model. Longifolene SOA particles are solid-like and all biogenic SOA sulfate mixtures exhibit a core–shell configuration (i.e.a sulfate-rich core coated with SOA). Biogenic SOA with or without sulfate formed ice at conditions expected for homogeneous ice nucleation, in agreement with respectiveTgand FDRH. α-pinene SOA coated soot particles nucleated ice above the homogeneous freezing temperature with soot acting as ice nuclei (IN). At lower temperatures the α-pinene SOA coating can be semisolid, inducing ice nucleation. Naphthalene SOA coated soot particles acted as ice nuclei above and below the homogeneous freezing limit, which can be explained by the presence of a highly viscous SOA phase. Our results suggest that biogenic SOA does not play a significant role in mixed-phase cloud formation and the presence of sulfate renders this even less likely. However, anthropogenic SOA may have an enhancing effect on cloud glaciation under mixed-phase and cirrus cloud conditions compared to biogenic SOA that dominate during pre-industrial times or in pristine areas.

scholarly journals Subglacial hydrology and the formation of ice streams

2014 ◽  
Vol 470 (2161) ◽  
pp. 20130494 ◽  
Author(s):  
T. M Kyrke-Smith ◽  
R. F Katz ◽  
A. C Fowler
Keyword(s):  
Ice Sheet ◽  
Water System ◽  
Coupled Model ◽  
Water Film ◽  
Mass Conservation ◽  
Ice Streams ◽  
Base Level ◽  
Ice Sheet Dynamics ◽  
Ice Water ◽  
Subglacial Meltwater

Antarctic ice streams are associated with pressurized subglacial meltwater but the role this water plays in the dynamics of the streams is not known. To address this, we present a model of subglacial water flow below ice sheets, and particularly below ice streams. The base-level flow is fed by subglacial melting and is presumed to take the form of a rough-bedded film, in which the ice is supported by larger clasts, but there is a millimetric water film which submerges the smaller particles. A model for the film is given by two coupled partial differential equations, representing mass conservation of water and ice closure. We assume that there is no sediment transport and solve for water film depth and effective pressure. This is coupled to a vertically integrated, higher order model for ice-sheet dynamics. If there is a sufficiently small amount of meltwater produced (e.g. if ice flux is low), the distributed film and ice sheet are stable, whereas for larger amounts of melt the ice–water system can become unstable, and ice streams form spontaneously as a consequence. We show that this can be explained in terms of a multi-valued sliding law, which arises from a simplified, one-dimensional analysis of the coupled model.

Self-diffusion of lignite/water under different temperatures and pressure: A molecular dynamics study

2016 ◽  
Vol 30 (01) ◽  
pp. 1550253 ◽  
Author(s):  
Xinjian Liu ◽  
Yu Jin ◽  
Congliang Huang ◽  
Jingfeng He ◽  
Zhonghao Rao ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Water System ◽  
Simulation Method ◽  
The Self ◽  
Dynamics Simulation ◽  
Low Rank ◽  
Self Diffusion ◽  
Change Mechanism ◽  
Different Temperatures ◽  
Temperature And Pressure

Temperature and pressure have direct and remarkable implications for drying and dewatering effect of low rank coals such as lignite. To understand the microenergy change mechanism of lignite, the molecular dynamics simulation method was performed to study the self-diffusion of lignite/water under different temperatures and pressure. The results showed that high temperature and high pressure can promote the diffusion of lignite/water system, which facilitates the drying and dewatering of lignite. The volume and density of lignite/water system will increase and decrease with temperature increasing, respectively. Though the pressure within simulation range can make lignite density increase, the increasing pressure showed a weak impact on variation of density.

scholarly journals Ice nucleation abilities of soot particles determined with the Horizontal Ice Nucleation Chamber

2018 ◽  
Vol 18 (18) ◽  
pp. 13363-13392 ◽  
Author(s):  
Fabian Mahrt ◽  
Claudia Marcolli ◽  
Robert O. David ◽  
Philippe Grönquist ◽  
Eszter J. Barthazy Meier ◽  
...  
Keyword(s):  
Particle Size ◽  
Water Saturation ◽  
Particle Surface ◽  
Water Vapor Sorption ◽  
Contact Angles ◽  
Ice Nucleation ◽  
Particle Surface Area ◽  
Soot Particles ◽  
Microphysical Properties ◽  
Homogeneous Freezing

Abstract. Ice nucleation by different types of soot particles is systematically investigated over the temperature range from 218 to 253 K relevant for both mixed-phase (MPCs) and cirrus clouds. Soot types were selected to represent a range of physicochemical properties associated with combustion particles. Their ice nucleation ability was determined as a function of particle size using relative humidity (RH) scans in the Horizontal Ice Nucleation Chamber (HINC). We complement our ice nucleation results by a suite of particle characterization measurements, including determination of particle surface area, fractal dimension, temperature-dependent mass loss (ML), water vapor sorption and inferred porosity measurements. Independent of particle size, all soot types reveal absence of ice nucleation below and at water saturation in the MPC regime (T>235 K). In the cirrus regime (T≤235 K), soot types show different freezing behavior depending on particle size and soot type, but the freezing is closely linked to the soot particle properties. Specifically, our results suggest that if soot aggregates contain mesopores (pore diameters of 2–50 nm) and have sufficiently low water–soot contact angles, they show ice nucleation activity and can contribute to ice formation in the cirrus regime at RH well below homogeneous freezing of solution droplets. We attribute the observed ice nucleation to a pore condensation and freezing (PCF) mechanism. Nevertheless, soot particles without cavities of the right size and/or too-high contact angles nucleate ice only at or well above the RH required for homogeneous freezing conditions of solution droplets. Thus, our results imply that soot particles able to nucleate ice via PCF could impact the microphysical properties of ice clouds.

scholarly journals Investigating the role of dust in ice nucleation within clouds and further effects on regional weather system over East Asia – Part I: model development and validation

2017 ◽  
Author(s):  
Lin Su ◽  
Jimmy C.H. Fung
Keyword(s):  
East Asia ◽  
Source Region ◽  
Model Development ◽  
Ice Nucleation ◽  
Dust Particles ◽  
Weather System ◽  
Microphysics Scheme ◽  
Ice Nuclei ◽  
Cloud Ice ◽  
Ice Water

Abstract. The GOCART–Thompson microphysics scheme, which couples the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model and aerosol-aware Thompson microphysics scheme, has been implemented in the Weather Research and Forecast model coupled with Chemistry (WRF-Chem), to quantify and evaluate the effect of dust on the ice nucleation process in the atmosphere by serving as ice nuclei. The performance of the GOCART-Thompson microphysics scheme in simulating the effect of dust in atmospheric ice nucleation is then evaluated over East Asia during spring in 2012, a typical dust-intensive season. Based upon the dust emission reasonably reproduced by WRF-Chem, the effect of dust on atmospheric cloud ice water content is well reproduced. With abundant dust particles serving as ice nuclei, the simulated ice water mixing ratio and ice crystal number concentration increases by one order of magnitude over the dust source region and downwind areas during the investigated period. The comparison with ice water path from satellite observations demonstrated that the simulation of cloud ice profile is substantially improved by applying the GOCART–Thompson microphysics scheme in the simulations. Additional sensitivity experiments are carried out to optimize the parameters in the ice nucleation parameterization in the GOCART–Thompson microphysics scheme, and the results suggest that the calibration factor in the ice nucleation scheme should be set to 3 or 4. Lowering the threshold relative humidity with respect to ice to 100 % for the ice nucleation parameterization leads to further improvement in cloud ice simulation.

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