Models for the determination of kinetic phase diagrams and kinetic phase separation domains

Los, J.; Heuvel, M. van den; Enckevort, W.J.P. van; Vlieg, E.; Oonk, H. A. J.; Matovic, Marija; Miltenburg, J.C. van

doi:10.1016/j.calphad.2005.12.002

Cited by 8 publications

(8 citation statements)

References 27 publications

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“…Monte Carlo simulations are used to qualitatively investigate ice segregation through two different diffusion mechanisms. The stochastic method employed here builds on the lattice-gas Monte Carlo technique used by Los et al (2006Los et al ( , 2007 and Cuppen & Herbst (2007). In the simulations CO 2 and H 2 O molecules are followed individually as a function of time, both position and environment, as they diffuse through the ice and desorb from it.…”

Section: Monte Carlo Simulationsmentioning

confidence: 99%

Quantification of segregation dynamics in ice mixtures

Öberg¹,

Fayolle²,

Cuppen

et al. 2009

A&A

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Context. The observed presence of pure CO 2 ice in protostellar envelopes, revealed by a double peaked 15 μm band, is often attributed to thermally induced ice segregation. The temperature required for segregation is however unknown because of lack of quantitative experimental data and this has prevented the use of ice segregation as a temperature probe. In addition, quantitative segregation studies are needed to characterize diffusion in ices, which underpins all ice dynamics and ice chemistry. Aims. This study aims to quantify the segregation mechanism and barriers in different H 2 O:CO 2 and H 2 O:CO ice mixtures. Methods. The investigated ice mixtures cover a range of astrophysically relevant ice thicknesses and mixture ratios. The ices are deposited at 16-50 K under (ultra-)high vacuum conditions. Segregation is then monitored, at 40-70 K in the CO 2 mixtures and at 23-27 K in the CO mixtures, through infrared spectroscopy. The CO 2 and CO band shapes are distinctly different in pure and mixed ices and can thus be used to measure the fraction of segregated ice as a function of time. The segregation barrier is determined using rate equations and the segregation mechanism is investigated through Monte Carlo simulations. Results. Thin (8-37 ML) H 2 O ice mixtures, containing either CO 2 or CO, segregate sequentially through surface processes, followed by an order of magnitude slower bulk diffusion. Thicker ices (>100 ML) segregate through a bulk process, which is faster than even surface segregation in thin ices. The thick ices must therefore be either more porous or segregate through a different mechanism, e.g. a phase transition, compared to the thin ices. The segregation dynamics of thin ices are reproduced qualitatively in Monte Carlo simulations of surface hopping and pair swapping. The experimentally determined surface-segregation rates follow the Ahrrenius law with a barrier of 1080 ± 190 K for H 2 O:CO 2 ice mixtures and 300 ± 100 K for H 2 O:CO mixtures. Though the barrier is constant with ice mixing ratio, the segregation rate increases with CO 2 concentration. Conclusions. Dynamical ice processes can be quantified through a combination of experiments and different model techniques and they are not scale independent as previously assumed. The derived segregation barrier for thin H 2 O:CO 2 ice mixtures is used to estimate the surface segregation temperature during low-mass star formation to be 30 ± 5 K. Both surface and bulk segregation is proposed to be a general feature of ice mixtures when the average bond strengths of the mixture constituents in pure ice exceeds the average bond strength in the ice mixture.

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Section: Monte Carlo Simulationsmentioning

confidence: 99%

Quantification of segregation dynamics in ice mixtures

Öberg¹,

Fayolle²,

Cuppen

et al. 2009

A&A

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“…It is best treated exactly in the case of a near-stationary process conditioned by e.g., Focker-Planck equation, Monte-Carlo method, or other stochastic process theory [3,4] requiring higher state of mathematics such as the linear kinetic segregation model by comparing its predictions with the results of Monte-Carlo simulations for both a well-mixing systems and a phase-separating systems. [20].…”

Section: Introductionmentioning

confidence: 95%

Kinetic phase diagrams as a consequence of sudden changing temperature or particle size

Šesták

2015

J Therm Anal Calorim

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The sphere of kinetic phase diagrams is reconsidered, while accentuating its specificity and practical impact when studying system under rapid changes of temperature (cooling). The meaning of temperature is discussed when measured during ultrafast quenching experiments. The apparent analogy between the temperature-dependent kinetic phase diagrams and those obtained for diminishing particle size is observed and investigated. Specific behavior of nanocomposites is explored regarding particle curvature, temperatures of transformation, dissolution, or phase separation.

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“…How the final equilibrium is reached exactly will mainly depend on the kinetics. 12 The driving force for such an LPE process is governed by bulk thermodynamics, and it enables the growth of thick bulklike structures.…”

Section: ■ Introductionmentioning

confidence: 99%

“…During this process, the compositions of both liquid and solid films can change, for which the latter can be exploited to grow composition-gradient films. How the final equilibrium is reached exactly will mainly depend on the kinetics . The driving force for such an LPE process is governed by bulk thermodynamics, and it enables the growth of thick bulklike structures.…”

Section: Introductionmentioning

confidence: 99%

Observation of Ultrathin Precursor Film Formation during Ge–Si Liquid-Phase Epitaxy from an Undersaturated Solution

et al. 2017

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Our in situ X-ray study shows that a silicon substrate in contact with an undersaturated In(Ge) solution is wetted by an approximately 1 nm thin germanium film, which does not grow any thicker. The results can be understood by the use of thickness-dependent correlated interfacial energies. This near-equilibrium heterogeneous interface structure marks the initial stage of crystal growth before the formation of bulk material, which can only form under conditions of supersaturation. This finding uncovers a fundamental aspect of the thermodynamics at solid-liquid interfaces relevant for understanding the transition from equilibrium to supersaturation and is of importance for nanoscale solution growth methods.

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Models for the determination of kinetic phase diagrams and kinetic phase separation domains

Cited by 8 publications

References 27 publications

Quantification of segregation dynamics in ice mixtures

Quantification of segregation dynamics in ice mixtures

Kinetic phase diagrams as a consequence of sudden changing temperature or particle size

Observation of Ultrathin Precursor Film Formation during Ge–Si Liquid-Phase Epitaxy from an Undersaturated Solution

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