Co-adsorption of benzene and CO on PtCo(1 1 1) surface at low coverage is studied using density functional theory calculations. We investigated the PtCo FCT alloy surface with a uniform distribution. The most favorable site for CO is top on a Pt atom whereas for benzene is an HCP hollow site (formed by 2 Pt atoms and 1 Co atom). The co-adsorption energy is -1.62 eV. The calculations indicate a CO molecule with a -4 tilt angle with the normal to the surface. The most important bond is Pt Cco, as revealed by overlap population analysis. A very small CO-benzene interaction is also detected. The vibrational frequencies of adsorbed benzene and CO were also computed. (C) 2013 Elsevier B.V. All rights reserved.