Local Order in AgAuCuPdPt High-Entropy Alloy Surfaces

Synthesis of high-entropy alloys often involvesheating precursors to above 1000 degrees C such that entropy stabilizationtakes effect. The resulting alloys are characterized by randomelement distribution at the bulk lattice positions. Surfaces mayhowever be more ordered, even at high temperatures. We explorethe local order at (111), (100), and (533) surfaces of theequimolar face-centered cubic (fcc) AgAuCuPdPt high-entropyalloy at high temperatures and thermal equilibrium. Wefind thatthe local order is significantly increased at the (100) surface and toa lesser extent at the (533) and (111) surfaces compared to bulkAgAuCuPdPt. The (100) surface both segregates with increasedamounts of Au and Ag and less Pd and Pt and has a more ordereddistribution of nearest-neighbor atom pairs. The (111) surfacesegregates with increased amounts of Au and Ag and less Cu, Pd, and Pt, but the nearest-neighbor distribution is mostly random.The (100)-type step edge of the (533) surface resembles the (100) surface. The degree of surface order seems linked to the structureensemble's energy distribution width, so we suggest that the width can be used to estimate the degree of order in high-entropy alloyswith minimal computational efforts.