Molecular dynamics simulations are performed to investigate the atomic distribution and the structure of platinum-cobalt nano-particles. Heating and cooling techniques are applied before getting equilibrated structures at 298 K. Both crystalline (fcc) and amorphous structures are partly observed depending on cooling rates. The atomic distributions in different regions of a bimetallic nanoparticle are analyzed. Although platinum tends to occupy surface and near-surface sites of the bimetallic nanoparticle, a complete segregation to form a core-shell structure is not observed. (c) 2005 Elsevier B.V. All rights reserved.