Surface segregation in Cr-Mn-Fe-Co-Ni high entropy alloys

The reactivity of the surface of multicomponent metals such as High Entropy Alloys (HEAs) is rapidly gaining importance for corrosion and catalytic applications, but the mechanisms of surface segregation in these complex materials are poorly understood. Here we investigate with ab initio calculations the segregation thermodynamics in the magnetic Cr-Mn-Fe-Co-Ni HEA in vacuum, in the presence of O at the surface, and in the oxide phase. We predict a weak segregation of Ni for Cr-, Mn-, and Fe-rich alloys in vacuum and a very strong segregation of Cr and Mn upon exposure to O.