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M W Cole

Publications and source records attributed to M W Cole.

8 recordsLinked to original sources
PubMed2003

Systematic model behavior of adsorption on flat surfaces.

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.

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PubMed2003

Phonon modes and heat capacity of monolayer films adsorbed in spherical pores.

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.

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PubMed2002

Simple model of capillary condensation in porous media.

We employ a simple model to describe the phase behavior of 4He and Ar in a hypothetical porous material consisting of a regular array of infinitely long, solid, parallel cylinders. We find that high porosity geometries exhibit two transitions: from vapor to film and from film to capillary condensed liquid. At low porosity, the film is replaced by a "necking" configuration, and for a range of intermediate porosity there are three transitions: from vapor to film, from film to necking and from necking to a capillary condensed phase.

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PubMed2001

Evidence concerning drying behavior of Ne near a Cs surface.

Using density functional and Monte Carlo methods, we have studied the properties of Ne adsorbed on a Cs surface, focusing on the region at and near saturated vapor pressure (SVP). In the case of Ne/Rb, the experimental data of Hess, Sabatini, and Chan are consistent with the calculations based on an ab initio fluid-substrate potential, while in the Ne/Cs case there is indication that the potential is approximately 9% too deep. In that case, the calculations yield partial drying behavior consistent with the experimental finding of depressed fluid density near the surface, above SVP. However, we find no evidence of a drying transition, a result consistent with the mean-field calculation of Ebner and Saam.

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PubMed2001

Dilation-induced phases of gases absorbed within a bundle of carbon nanotubes.

A study is presented of the effects of gas (especially H2) absorption within the interstitial channels of a bundle of carbon nanotubes. The ground state of the system is determined by minimizing the total energy, which includes the molecules' interaction with the tubes, the intertube interaction, and the molecules' mutual interaction (which is screened by the tubes). The consequences of swelling include a reduced threshold pressure for gas uptake and a 2.7% increase in the tubes' breathing mode frequency.

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