Theory of repulsive charged colloids in slit-pores

9 pags., 8 figs., 1 tab.Using classical density functional theory (DFT) we analyze the structure of the density profiles and solvation pressures of negatively charged colloids confined in slit pores. The considered model, which was already successfully employed to study a real colloidal (silica) suspension [S. H. L. Klapp, Phys. Rev. Lett. 100, 118303 (2008)10.1103/PhysRevLett.100.118303], involves only the macroions which interact via the effective Derjaguin-Landau-Verwey-Overbeek (DLVO) potential supplemented by a hard core interaction. The solvent enters implicitly via the screening length of the DLVO interaction. The free energy functional describing the colloidal suspension consists of a hard sphere contribution obtained from fundamental measure theory and a long range contribution which is treated using two types of approximations. One of them is the mean field approximation (MFA) and the remaining is based on Rosenfelds perturbative method for constructing the Helmholtz energy functional. These theoretical calculations are carried out at different bulk densities and wall separations to compare finally to grand canonical Monte Carlo simulations. We also consider the impact of charged walls. Our results show that the perturbative DFT method yields generally qualitatively consistent and, for some systems, also quantitatively reliable results. In MFA, on the other hand, the neglect of charge-induced correlations leads to a breakdown of this approach in a broad range of densities. © 2012 American Institute of Physics.A.G. and N.G.A. acknowledge financial support from the Dirección General de Investigación Científica y Técnica under Grant No. FIS2010-15502, and from the Dirección General de Universidades e Investigación de la Comunidad de Madrid under Grant No. S2009/ESP-1691 and Program MODELICO-CM. S.G. and S.H.L.K. would like to thank the German Research Foundation (DFG) for financial support within the Collaborative Research Center (CRC) 951 “Hybrid Inorganic/organic systems for Optoelectronics” and the International Graduate School (IRTG) 1524 “Selfassembled soft-matter nanostructures at interfaces.