Growth and alloy formation of Fe on flat and stepped Pt substrates

Atomistic modeling of subsurface Fe-Pt alloy formation upon deposition of Fe on Pt(1 0 0), Pt(1 1 1), and vicinal Pt(9 9 7) substrates using the BFS method for alloys is presented. The simulation results indicate preference for Fe atoms to occupy sites in the Pt subsurface layers and form an ordered alloy phase upon deposition on a low-index Pt surface. This behavior results in Pt surface segregation leading to nucleation of 3D Pt islands. A similar atom-by-atom analysis of Fe deposition on a stepped Pt(9 9 7) substrate indicates that Fe atoms prefer decoration of Pt step edges prior to formation of the ordered Fe-Pt surface alloy, where the ordered alloy is observed to form at the edges of the monoatomic surface steps. The pathway for Fe-Pt subsurface alloy formation is explained by a simple picture emerging from the competition between BFS strain and chemical energy contributions.