Shear-induced phase transitions in fluids confined between chemically decorated substrates

Authors
Citation
H. Bock et M. Schoen, Shear-induced phase transitions in fluids confined between chemically decorated substrates, J PHYS-COND, 12(8), 2000, pp. 1569-1594
Citations number
68
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
JOURNAL OF PHYSICS-CONDENSED MATTER
ISSN journal
09538984 → ACNP
Volume
12
Issue
8
Year of publication
2000
Pages
1569 - 1594
Database
ISI
SICI code
0953-8984(20000228)12:8<1569:SPTIFC>2.0.ZU;2-Q
Abstract
In this paper we investigate the phase behaviour of a 'simple' fluid confin ed to a slit of nanoscopic width s(z) by chemically decorated, plane-parall el substrates consisting of slabs of weakly and strongly adsorbing solid wh ich alternate in the x-direction with period s(x). In the y-direction the s ubstrates, occupying the half-spaces -infinity less than or equal to z less than or equal to -s(z)/2 and s(z)/2 less than or equal to z less than or e qual to infinity, are translationally invariant. On account of the interpla y between confinement (i.e., s(z)) and chemical decoration, three fluid pha ses are thermodynamically permissible, namely (inhomogeneous) gaslike and l iquidlike phases and 'bridge phases' consisting of high(er)-density fluid o ver the 'strong' part which alternates in the x-direction with low(er)-dens ity fluid over the 'weak' part of the substrate. In the x-y plane the two a re separated by an interface. Because of their lateral inhomogeneity, bridg e phases can be exposed to a shear strain alpha s(x) (0 less than or equal to alpha less than or equal to 1/2) by misaligning the substrates in the x- direction. Depending on the thermodynamic state of the confined fluid and d etails of the chemical decoration, shear-induced first-order phase transiti ons are feasible during which a bridge phase may be transformed into either a gaslike (evaporation) or a liquidlike phase (condensation). These phase transitions are studied by computing phase diagrams as functions of ols, fo r a meanfield lattice-gas model. The lattice-gas calculations are amended b y grand canonical ensemble Monte Carlo simulations of a fluid confined betw een chemically decorated substrate surfaces. The combination of the two set s of data reveals that the lattice-gas model captures correctly key charact eristics of shear-induced first-order phase transitions in this rather comp lex system despite its mean field character.