Solid phase of Krypton on the exterior of individual single-walled carbon nanotubes

We have computed the adsorption of Krypton in a closed single-walled carbon nanotube using the method of Grand Canonical Monte Carlo. Our results indicate evidence of an incommensurate solid formed at high pressure and low temperature (T<85K), before the formation of a second layer. The solid melts above that temperature. Our simulations are in good agreement with novel experimental results for adsorption in individual carbon nanotubes.

To wet or not to wet: that is the question

Wetting transitions have been predicted and observed to occur for various combinations of fluids and surfaces. This paper describes the origin of such transitions, for liquid films on solid surfaces, in terms of the gas-surface interaction potentials V(r), which depend on the specific adsorption system. The transitions of light inert gases and H2 molecules on alkali metal surfaces have been explored extensively and are relatively well understood in terms of the least attractive adsorption interactions in nature. Much less thoroughly investigated are wetting transitions of Hg, water, heavy inert gases and other molecular films. The basic idea is that nonwetting occurs, for energetic reasons, if the adsorption potentials well-depth D is smaller than, or comparable to, the well-depth of the adsorbate-adsorbate mutual interaction. At the wetting temperature, Tw, the transition to wetting occurs, for entropic reasons, when the liquids surface tension is sufficiently small that the free energy cost in forming a thick film is sufficiently compensated by the fluid- surface interaction energy. Guidelines useful for exploring wetting transitions of other systems are analyzed, in terms of generic criteria involving the simple model, which yields results in terms of gas-surface interaction parameters and thermodynamic properties of the bulk adsorbate.

Effects of substrate relaxation on adsorption in pores

Fluids in porous media are commonly studied with analytical or simulation methods, usually assuming that the host medium is rigid. By evaluating the substrates response (relaxation) to the presence of the fluid we assess the error inherent in that assumption. One application is a determination of the ground state of 3He in slit and cylindrical pores. With the relaxation, there results a much stronger cohesion than would be found for a rigid host. Similar increased binding effects of relaxation are found for classical fluids confined within slit pores or nanotube bundles.