length First-principles study of five Fe-based high entropy alloys

The mechanical and magnetic properties of three equiatomic (FeTiVNi, FeCoVNi, and FeTiGeCo), and two non-equiatomic (FeTiGe 0.75 Se 0.25 Co and FeTiGe 0.5 Se 0.5 Co) high entropy alloys (HEAs) were considered by density functional theory. The results show that when Ti is replaced with Co in the FeTiVNi high entropy alloy, its structure transforms from body-centred cubic into face-centred cubic. On the other hand, when V and Ni are replaced by Ge and Ti in the FeCoVNi alloy, the structure of FeTiGeCo alloy remains bodycentred cubic. The formation energy and phonon dispersion results show that the considered high entropy alloys are thermodynamically and dynamically stable. Their elastic constants satisfy Born's stability condition, indicating their mechanical stability. Since FeTiGeCo alloy only marginally meets this stability condition, we also investigated its Se-doped structures, FeTiGe 0.75 Se 0.25 Co and FeTiGe 0.5 Se 0.5 Co, both of which are found to be mechanically stable. Poisson's and Pugh's ratios imply that all the considered high entropy alloys are ductile. Analysis of the electronic structure from the density of states and band structure reveals that these alloys have a metallic character. The highest magnetic moment per atom of 18.752 mu(B) was obtained for FeCoVNi, with main contributions from Fe and Co atoms. Due to their high magnetic moments, considered high entropy alloys may have potential applications as magnetic materials in power electronics.