First-principles calculation of lattice distortions in four single phase high entropy alloys with experimental validation

Exceptional properties of high entropy alloys (HEAs) are attributed to the disordered random solid solution of multiple alloying elements. Despite numerous studies, the fundamental understanding at the electronic and atomic levels is still missing. We report a comparative study of four fcc HEAs of NiFeCoCr and NiFeCoCrX (X = Mn, Cu, or Pd) based on ab initio calculations using large supercells with 500 atoms in equal composition. After fully optimizing their structures using the VASP package, their electronic structure, interatomic bonding, partial charge distribution, and mechanical properties are calculated and compared, revealing the intricate interdependence among them. A novel parameter based on the quantum mechanical metric for internal cohesion, the total bond order density (TBOD), is used to interpret the calculated properties. The highest TBOD is found in Cantor alloy NiFeCoCrMn but lower in NiFeCoCrPd. The atomic radii vary depending on their local chemical environment. The resulting lattice distortions is validated experimentally in NiFeCoCrMn and NiFeCoCrPd. Moreover, modeling of Cu and Pd clustering in the supercell shows they have lower total energy in agreement with the observation of Cu-enhanced nanoparticipates in NiFeCoCrCu and Pd-induced concentration wave in NiFeCoCrPd HEAs. (c) 2021 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

A comparative study of high entropy alloys using ab initio calculations reveals intricate interdependence among electronic structure, interatomic bonding, partial charge distribution, and mechanical properties. The novel parameter of total bond order density (TBOD) is used to interpret the properties, with highest TBOD found in Cantor alloy NiFeCoCrMn. Experimental validation shows lattice distortions in NiFeCoCrMn and NiFeCoCrPd based on atomic radii variations. Modeling of Cu and Pd clustering in the supercell demonstrates lower total energy, consistent with observed enhancements in Cu and Pd-induced concentration wave in HEAs.