Thermodynamics of a fluid confined to a slit pore with structured walls

Journal Article · Wed Jun 15 04:00:00 EDT 1994 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.466668· OSTI ID:7116591

Diestler, D J ^[1]; Schoen, M ^[2]; Curry, J E; Cushman, J H ^[3]

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1. Department of Agronomy, Keim Hall, University of Nebraska-Lincoln, Lincoln, Nebraska 68503-0915 (United States)
2. Institut fuer Theoretische Physik, Technische Universitaet Berlin, Hardenbergstrasse 36, 10623 Berlin (Germany)
3. Lilly Hall of Life Sciences, Purdue University, West Layfayette, Indiana 47907 (United States)

In this article we extend our previous thermodynamic analysis of films confined to slit pores with smooth walls (i.e., plane--parallel solid surfaces without molecular structure) to the situation in which the walls themselves possess structure. Structured-wall models are frequently employed to interpret experiments performed with the surface forces apparatus (SFA), in which thin films (1--10 molecular diameters thick) are subjected to shear stress by moving the walls laterally over one another at constant temperature, chemical potential, and normal stress or load. The periodic structure of the walls is reflected in a periodic variation of the shear stress with the lateral alignment (i.e., shear strain) of the walls. We demonstrate by means of a solvable two-dimensional model that the molecular length scale imposed by the structure of the walls precludes the derivation of a simple mechanical expression for the grand potential analogous to that which holds in the smooth-wall case. This conclusion is borne out by the results of a grand-canonical Monte Carlo simulation of the three-dimensional prototypal model consisting of a Lennard-Jones (12,6) fluid confined between fcc (100) walls. Criteria for the thermodynamic stability of thin films confined by structured walls are derived and applied to the SFA.

• DOE Contract Number: FG02-85ER60310
• OSTI ID: 7116591
• Journal Information: Journal of Chemical Physics; (United States), Journal Name: Journal of Chemical Physics; (United States) Vol. 100:12; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

665000* -- Physics of Condensed Matter-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CONFINEMENT
EQUATIONS
FILMS
FLUIDS
LENNARD-JONES POTENTIAL
MATHEMATICAL MODELS
MECHANICAL PROPERTIES
MOLECULAR STRUCTURE
MOTION
POTENTIALS
SHEAR PROPERTIES
STABILITY
STRESSES
TEMPERATURE DISTRIBUTION
THERMODYNAMICS
THIN FILMS
WALLS