title: Nonzero ionic size and charge-correlation forces between fluid membranes.
abstract: We present a theoretical approach to charge-correlation attractions between like-charged membranes with neutralizing counterions assumed to be localized to the membrane surface. In particular, we study the effect of nonzero ionic sizes on the attraction by treating the membrane charges (both backbone charges and localized counterions) as forming a two-dimensional ionic fluid of hard spheres of the same diameter D . Using a two-dimensional Debye-Huckel approach to this system, we examine how ion sizes influence the attraction. We find that the attraction gets stronger as surface charge densities or counterion valency increase, consistent with long-standing observations. Our results also indicate a nontrivial dependence of the attraction on separations h: The attraction is enhanced by ion sizes for intermediate h ranges, while it crosses over to the known D -independent universal behavior as h-->infinity; it remains finite as h-->0, as expected for a system of finite-sized ions.
authors.affiliation: Department of Physics, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1.
authors.forename: Yang
authors.initials: Y
authors.lastname: Li
authors.forename: Bae-Yeun
authors.initials: BY
authors.lastname: Ha