Heras, Daniel de lasMartínez-Ratón, YuriVelasco, Enrique2010-02-232010-02-232010-02Physical Review E 81, 021706 (2010)1539-3755https://hdl.handle.net/10016/697612 pages, 13 figures.-- PACS nrs.: 64.70.M-, 61.30.Hn, 61.20.Gy, 64.75.Xc.-- ArXiv pre-print available at: http://arxiv.org/abs/1002.0512The surface phase behavior of binary mixtures of colloidal hard rods in contact with a solid substrate (hard wall) is studied, with special emphasis on the region of the phase diagram that includes the smectic A phase. The colloidal rods are modeled as hard cylinders of the same diameter and different lengths, in the approximation of perfect alignment. A fundamental-measure density functional is used to obtain equilibrium density profiles and thermodynamic properties such as surface tensions and adsorption coefficients. The bulk phase diagram exhibits nematic-smectic and smectic-smectic demixing, with smectic phases having different compositions; in some cases they are microfractionated. The calculated surface phase diagram of the wall-nematic interface shows a very rich phase behavior, including layering transitions and complete wetting at high pressures, whereby an infinitely thick smectic film grows at the wall via an infinite sequence of stepwise first-order layering transitions. For lower pressures complete wetting also obtains, but here the smectic film grows in a continuous fashion. Finally, at very low pressures, the wall-nematic interface exhibits critical adsorption by the smectic phase, due to the second-order character of the bulk nematic-smectic transition.application/pdfeng© The American Physical Society[PACS] Transitions in liquid crystals[PACS] Surface phenomena: alignment, anchoring, anchoring transitions, surface-induced layering, surface-induced ordering, wetting, prewetting transitions, and wetting transitions[PACS] Theory and models of liquid structure[PACS] Phase separation and segregation in colloidal systemsresearch articleMatemáticas10.1103/PhysRevE.81.021706open access