First principle study of magnetism and vacancy energetics in a near equimolar NiFeMnCr high entropy alloy

Abstract

We report the results of ab initio calculations of a novel NiFeMnCr high entropy alloy (HEA) with potential applications as a high performance structural material. The bulk and defect property variations due to chemical disordering and magnetic frustration have been studied using both supercell and coherent potential approximation-based techniques. While magnetic frustration due to the presence of multiple 3d transition metals can severely affect the accuracy of vacancy formation energy in first-principles calculations, this effect should be suppressed at intermediate and high temperatures. An efficient approach to evaluate the chemical potential in HEA is constructed and implemented. Vacancy formation energies are computed based on the chemical potential. The statistical distribution of formation energies is weakly dependent upon the chemical identity of the vacancy. On the other hand, the calculated vacancy migration energies show that Fe is more likely to have a large migration barrier than Cr, Mn, or Ni. Finally, atomic-level stresses are computed. A qualitative model to explain the elemental segregation trend in HEA is built upon the atomic-level stress calculation results and provides a reasonable qualitative agreement with ion irradiation experimental data of a NiFeMnCr HEA.

Thermal Vacancies in High-Entropy Alloys

“…Table 2 Assessed RedlichKister parameters (J mol ¹1 ) used in the present work: CoCr, 35) CoFe, 36) CoMn, 37) CoNi, 38) CrFe, 39,40) Cr Mn, 41) CrNi, 42) FeMn, 43) FeNi, 44) and MnNi. 45) Experimental data [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] Average Calculations [33][34][35] Vacancy formation enthalpy,…”

Corrosion and Thermal Stability of CrMnFeNi High Entropy Alloy in Molten FLiBe Salt

“…This significant change indicates the higher rates of Mn dissolution in the salt, while Ni experienced slight reduction in both cases. The diffusion of Mn is likely occur via vacancy diffusion 19,20 , but no significant change in the porosity concentration was observed after the corrosion test.…”

Machine Learning Based Methodology to Predict Point Defect Energies in Multi-Principal Element Alloys

“…For example, using density functional theory (DFT) calculations, Guan et al (Guan et al, 2020) showed that the vacancy formation energy ranges between 1.62 eV and 2.03 eV in NiCrCo, 1.62 eV-2.04 eV in NiFeCrCo, and 1.51 eV-2.72 eV in NiFeCrCoMn, respectively. Similarly, Zhao et al (2018) and Li et al (2019) showed that there is large variation in the vacancy migration energies, i.e., 0.35 eV-1.24 eV in NiCrCo, 0.36 eV-1.34 eV in NiFeCrCo, and 0.55 eV-1.68 eV in NiFeCrMn, respectively.…”

“…Due to the random distribution of various elements, a complexity arises where each lattice site has unique nearest-neighbor chemical environment and bond lengths that lead to distinctly different point defect energies. As a result, there are large variations in defect energies even within a given alloy composition (Del Rio et al, 2011;Piochaud et al, 2014;Zhang et al, 2015Zhang et al, , 2017Zhao et al, 2016Zhao et al, , 2018Li et al, 2019;Guan et al, 2020;Arora et al, 2021). This is in contrast to essentially a single defect energy value in conventional and/or dilute alloys.…”