Monte Carlo study of structural ordering of Lennard-Jones fluids confined in nanochannels.

We investigate quantitatively the ordering of Lennard-Jones fluids confined in a thin and infinitely long nanochannel with square cross section. The most probable spatial configurations of the atoms were examined by Monte Carlo simulations, and the order parameter was calculated. The effect of the various parameters, such as the wall-fluid attractive interaction, the size of constriction, and the temperature, was studied. The results indicate that for strong wall-fluid interactions and small constrictions, the ordering of the fluid particles is almost perfect. Geometrical mismatch, as well as increasing the system's temperature, deteriorates the ordering phenomenon, even for very small openings. We observe a nontrivial trend in the dependence of the order parameter on the size of the opening of the channel with a linear size smaller than five atomic layers. We also examined the rearrangements of the fluid's atoms in more symmetrical pores--slitlike pores and cylindrical nanopores--and discuss their similarities and differences with the square channels.