ABSTRACT
We present Monte Carlo simulation results for strongly coupled dipolar fluids, such as ferrofluids, confined to a narrow slit pore accommodating only a few layers of particles. Our results show that the ferromagnetic ordering observed in dense bulk systems and in thick fluid films persists down to nanoscopic wall separations where the system consists of only 3 monolayers. The ferromagnetic transition density in these systems approaches experimentally accessible values. For even smaller wall separations, we observe stripelike defects and finally the breakdown of orientational ordering for systems close to the two-dimensional limit. Our results for the liquid phase are supported by simulations starting from quasicrystalline soft-sphere configurations.
ABSTRACT
The adsorption geometry of various gases on top of a C60 monolayer is investigated. The potential energy experienced by an adsorbate atom in the vicinity of a C60 molecule consists of Lennard-Jones interactions integrated over the spherical surface of the molecule. The adsorption potential exhibits strongly attractive sites which lead to a commensurate phase. The next adsorption sites are assumed on the basis of the symmetries of the triangular C60 array. The competition between different adsorption phases is solved by energy minimization. The onset pressure of each phase is computed and compared with experimental data for Kr on top of a C60 monolayer.
ABSTRACT
A low density film on a flat surface is described by an expansion involving the first four virial coefficients. The first coefficient (alone) yields the Henry's law regime, while the next three terms in the expansion correct for the effects of adsorbate-adsorbate interactions, computed within the two-dimensional approximation (a film confined nearly to a plane). The results permit exploration of the idea of universal adsorption behavior, which is compared with experimental data for a number of systems. The idea works well, in general, justifying a general model of adsorption at low to moderate coverage.
ABSTRACT
We examine the hydrodynamic phonon spectrum of a monolayer film adsorbed on the wall of a spherical pore. Due to the boundary conditions, the monolayer film exhibits a discrete phonon spectrum. The corresponding density of states per unit frequency is thus a set of delta functions, and the heat capacity exhibits Arrhenius behavior at low temperatures. At high temperatures, the heat capacity approaches the C approximately T2 behavior of a two-dimensional monolayer film. Our results for the spherical surface film are compared to previous calculations for films confined to a cylindrical surface.
