Coarsening in fluid phase transitions

Abstract

We review the understanding of the kinetics of fluid phase separation in various space dimensions. Morphological differences, percolating or disconnected domains, based on overall composition in a binary liquid or on density in a vapor-liquid system, are discussed. Depending upon the morphology, various possible mechanisms for domain growth are pointed out and discussions of corresponding theoretical predictions are provided. On the computational front, useful models and simulation methodologies are presented. Theoretically predicted growth laws have been tested via molecular dynamics simulations of vapor-liquid transitions. In the case of a disconnected structure, the mechanism has been confirmed directly.© 2015 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved. r é s u m éNous passons en revue la compréhension de la cinétique de séparation de phases fluides dans diverses dimensions d'espace. Les différences morphologiques, les domaines de percolation ou déconnectés, basés sur la composition totale binaire ou sur la densité dans un système vapeur-liquide, sont discutés. Selon la morphologie, les différents mécanismes possibles sont présentés et les prédictions théoriques correspondantes discutées. Du côté du calcul par ordinateur, des modèles utiles et des méthodes de simulation sont présentées. Des lois de croissance prédites théoriquement ont été testées au moyen de simulations de dynamique moléculaire des transitions vapeur-liquide. Dans le cas d'une structure déconnectée, le mécanisme a été confirmé directement.

Power-law coarsening in network-forming phase separation governed by mechanical relaxation

“…First, we consider the growth exponent ν = 1/2 observed previously by MD simulations of spinodal decomposition. This exponent was reported for 2D gas–liquid spinodal decomposition of single-component fluids 23 , 52 – 54 . For this case, the growth exponent of 1/2 was ascribed to the interface-limited (or, ballistic) evaporation–condensation mechanism, where the transport of molecules is kinematic (or, interface-limited) rather than diffusive 1 , 52 , 55 , 56 .…”

Controlling cluster size in 2D phase-separating binary mixtures with specific interactions

“…For 2D solid binary mixtures, an exponent α = 1/5 was proposed when growth is dominated by cluster diffusion and coalescence, at temperatures well below the critical one 31,32 . The so-called Lifshitz-Slyozov mechanism, akin to Ostwald ripening and due to evaporation and recondensation of single particles, should instead give α = 1/3, irrespective of dimensionality 30,33,46 . A richer phenomenology has been reported for fluid systems, for which (still in 2D) a crossover from α = 1/3, to 1/2, to 2/3 is expected 30,34,47,48 , although values of α between 1/4 and 1/3 have also been observed when hydrodynamics is suppressed 49,50 .…”

“…The so-called Lifshitz-Slyozov mechanism, akin to Ostwald ripening and due to evaporation and recondensation of single particles, should instead give α = 1/3, irrespective of dimensionality 30,33,46 . A richer phenomenology has been reported for fluid systems, for which (still in 2D) a crossover from α = 1/3, to 1/2, to 2/3 is expected 30,34,47,48 , although values of α between 1/4 and 1/3 have also been observed when hydrodynamics is suppressed 49,50 . Our system is neither fully solid, because clusters can diffuse and coalesce, nor fully fluid, as hydrodynamic drag effects are negligible at our low densities.…”

“…Our system is neither fully solid, because clusters can diffuse and coalesce, nor fully fluid, as hydrodynamic drag effects are negligible at our low densities. In addition the morphology of the clusters and the stoichiometry can affect growth 30,47 .…”

Droplet growth during vapor-liquid transition in a 2D Lennard-Jones fluid

“…On the other hand, in the nucleation and growth regime, close to the coexistence curve, one of the phases (liquid or vapor) fails to percolate [12,13,17,19,20]. There has been significant recent interest in the kinetics with such morphology [17,[19][20][21][22][23][24][25][26][27][28][29]. For overall density close to the vapor branch, circular or spherical liquid droplets, depending upon the system dimension (d), nucleate [30][31][32].…”