NANOPHASE COEXISTENCE AND SIEVING IN BINARY-MIXTURES CONFINED BETWEENCORRUGATED WALLS

The grand canonical Monte Carlo method is used to study a binary mixtu re of Lennard-Jones atoms confined to a corrugated slit micropore whic h is in thermodynamic equilibrium with its bulk phase counterpart. The micropore has atomically structured walls; one of the which possesses nanoscale structure in the form of rectilinear grooves (corrugation). The grooved surface divides the confined fluid him into two strip sha ped regions, that inside and that outside the grooves. Transverse soli dlike order in the him gives rise to shear stress. Transverse order co upled with packing restrictions give rise to a difference between the pore and bulk fluid mixture compositions. Solidlike order may appear;w ithin the grooves only, outside the grooves only, or in both regions s imultaneously. As the relative alignment of the walls is shifted the p ore fluid undergoes freeze-thaw cycles in one or both regions with ass ociated changes in the shear stress and pore fluid composition. The de gree of transverse order in the film is less than would be expected in a pure Lennard-Jones film and fluid-solid phase transitions are gradu al as opposed to sudden as seen in pure Lennard-Jones films. The magni tude of the shear stress is greatest when a fluid-solid phase transiti on occurs in both regions of the pore. (C) 1995 American Institute of Physics.