Casimir amplitudes and capillary condensation of near-critical fluids between parallel plates: Renormalized local functional theory

Ryuichi Okamoto, Akira Onuki

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38 Citations (Scopus)

Abstract

We investigate the critical behavior of a near-critical fluid confined between two parallel plates in contact with a reservoir by calculating the order parameter profile and the Casimir amplitudes (for the force density and for the grand potential). Our results are applicable to one-component fluids and binary mixtures. We assume that the walls absorb one of the fluid components selectively for binary mixtures. We propose a renormalized local functional theory accounting for the fluctuation effects. Analysis is performed in the plane of the temperature T and the order parameter in the reservoir ψ . Our theory is universal if the physical quantities are scaled appropriately. If the component favored by the walls is slightly poor in the reservoir, there appears a line of first-order phase transition of capillary condensation outside the bulk coexistence curve. The excess adsorption changes discontinuously between condensed and noncondensed states at the transition. With increasing T, the transition line ends at a capillary critical point T=T c ca slightly lower than the bulk critical temperature T c for the upper critical solution temperature. The Casimir amplitudes are larger than their critical point values by 10-100 times at off-critical compositions near the capillary condensation line.

Original languageEnglish
Article number114704
JournalJournal of Chemical Physics
Volume136
Issue number11
DOIs
Publication statusPublished - Mar 21 2012
Externally publishedYes

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parallel plates
Condensation
condensation
Binary mixtures
binary mixtures
Fluids
fluids
critical point
Contacts (fluid mechanics)
Temperature
critical temperature
Phase transitions
Adsorption
adsorption
temperature
curves
profiles
Chemical analysis

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

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