Liquids at interfaces: what can a theorist contribute?

Abstract

Reviews some recent theoretical and computer simulation studies of simple atomic fluids adsorbed at structureless substrates. Emphasis is placed on phase transitions, especially the various types of wetting transition. Criticality is associated with capillary-wave-like fluctuations in a continuously growing wetting film. This is of a subtle nature, which is best understood in terms of the pairwise correlation function of the fluid. Other surface phase transitions, such as prewetting and layering, occur out of bulk coexistence. Theory suggests that for sufficiently attractive substrates a sequence of first-order transitions, corresponding to the growth of new adsorbed liquid layers, should occur as the pressure of the bulk gas increases towards saturation at temperatures not too far above the bulk triple point. The extent to which such behaviour is found in adsorption experiments is discussed. The authors also argue that a simple fluid confined between two parallel hard-walls can exhibit surprisingly rich equilibria.

Nonequilibrium molecular dynamics simulations of nanoconfined fluids at solid-liquid interfaces

“…This is a manifestation of the Kelvin shift of the bulk coexistence curve, which occurs due to the spatial confinement of the fluid, 59 reflecting the higher degree of effective confinement in the hydrophobic case due to the repulsive wall layer. In fact, the underlying physics can give rise to rich phase equilibria and wetting transitions for capillaries, 60 grooves, 61,62 and more general geometries such as steps and wedges. 63 We note that in the more confined case presented in Fig.…”

Classical density functional study of wetting transitions on nanopatterned surfaces

“…Figure 1(a) shows a plot of the coexisting adsorptions as we move along the pre-wetting lines of both materials. The maximum of each curve corresponds to the pre-wetting critical point at which thin-thick coexistence ends [1,5,40]. The divergence of the thicker film adsorption near T w is controlled by the long-range tails of the intermolecular forces.…”

Complete prewetting

“…The thermodynamics and phase transitions of fluids inside slit pores is very well understood [39,40,[59][60][61]. The main effect of the finite size is to shift the bulk coexistence curve -an effect known as capillary condensation.…”