ON THE THERMODYNAMIC STABILITY OF CONFINED THIN-FILMS UNDER SHEAR

Thin films of monatomic fluid constrained between two plane-parallel s tructured solid walls have been modeled by Monte Carlo simulation unde r conditions (fixed temperature, chemical potential, and normal stress or load) prevailing in high-precision measurements of surface forces. Several states of the film, corresponding to different numbers of lay ers of fluid parallel with the walls, are generally consistent with th ese conditions, but only one is thermodynamically stable; the others a re metastable. When the walls are properly aligned, epitaxial solid ph ases are stable. These melt under shear, eventually becoming metastabl e, whereupon a drainage (or imbibition) transition occurs, leading to a stable phase with fewer (or more) layers.