Size selectivity of narrow pores

The selectivity of micropores and ion channels is examined fur simple pore topologies within the framework of density functional theory of highly conf ined fluids. In an infinite cylindrical pore purely steric (excluded volume ) effects are shown to lead to strong, nontrivial size selectivity, which i s highly sensitive to the pore radius. A crude modeling of electrostatic ef fects does not alter the relative absorbance of Na+ and K+ ions in a signif icant way.