Surface segregation in Pt25Rh75 alloys studied by Monte Carlo simulations and the modified embedded atom method

In this work, surface segregation in Pt25Rh75 alloys is studied by Monte Carlo (MC) simulations, combined with the modified embedded atom method (MEAM). First, for a more accurate description of the interatomic interactions, new MEAM parameters are derived, based on ab initio density functional theory (DFT) data. Subsequently, the temperature dependent surface segregation to the low index single crystal surfaces of a Pt25Rh75 alloy is calculated with this new parameter set. The simulation results are then confronted with available experimental and theoretical work. A peculiarity of the Pt-Rh system is the possible presence of a bulk demixing region at lower temperatures. This demixing behaviour is still contested up to now. Our results are in contradiction with such a phase separation behaviour.