Stability and Thermodynamics Properties of CrFeNiCoMn/Pd High Entropy Alloys from First Principles

In this study, we focus on structural and thermodynamics properties, as well as phase stability of quinary CrFeCoNiMn and CrFeCoNiPd high-entropy alloys (HEA) for both equiatomic and non-equiatomic compositions. CrFeCoNiMn (Cantor alloy) is a widely studied fcc alloy, while CrFeCoNiPd is a newly reported fcc alloy, being synthesized by intentionally substituting Mn in Cantor alloy by Pd which has a markedly different atomic size and electronegativity from the other constituent elements and has been achieved the better mechanical properties than Cantor alloy in experiments. DFT-based integrated approaches are conducted on these two quinary systems to calculate the structural, electronic structure and magnetic properties at zero K, as well as the free energies as function of temperature including vibrational, configurational mixing entropy and thermal electronic effects. Various SQS models with about 200 atoms were created to simulate the equiatomic HEA and a special non-equiatomic HEA where a principal element has a rather high concentration while other four kinds of element have equal lower concentrations. Comparison between Mn- and Pd-HEAs in both equiatomic and non-equiatomic compositions shows that the stability of Mn- and Pd-HEAs at zero K and finite temperature are dominated by different mechanisms, this can explain the recent experimental observation that a pronounced spatial fluctuation in atomic fraction is much wider in Pd-HEA rather than in Mn-HEA.