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
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.