Ab initio investigation of structural stability, magnetic ground state, and mechanical anisotropy of the CoCrFeNi high-entropy alloy

The equiatomic face-centered cubic (FCC) CoCrFeNi high-entropy alloy acts as a fundamental matrix for advanced alloys; however, its local magnetic interactions and the resulting directional mechanical behavior remain elusive due to computational limitations in modeling large random solid solutions. This study overcomes these barriers by employing a high-fidelity compact ordered cell (SSOS) combined with first-principles calculations (DFT + U) to systematically investigate its structural, electronic, magnetic, and mechanical properties. The calculated lattice parameter ( a 0 = 3.55 Å ) and the negative mixing enthalpy ( ∆ H mix = − 23.81 kJ / mol ) confirm high thermodynamic stability. Methodological consistency is validated by the agreement between the bulk modulus derived from the Birch-Murnaghan equation of state ( B 0 = 188 GPa ) and that obtained independently from the elastic constants ( B = 188.7 GPa ). Spin density analysis reveals that chromium exhibits local ferrimagnetic (antiparallel) coupling within the ferromagnetic Fe-Co-Ni matrix. This behavior induces magnetic frustration, suppressing the total magnetic moment to 0.76 μ B atom , while strong directional d − d hybridization positions the Fermi level within a minority-spin pseudogap. Regarding mechanical behavior, the alloy is intrinsically ductile (Pugh's ratio of 2.00) but exhibits extreme directional elastic anisotropy ( A Z = 3.60 ), with maximum stiffness ( 369.4 GPa ) along the close-packed 〈111〉 directions. By effectively representing complex local atomic environments without the high computational cost of large supercells, these results establish a direct correlation between electronic-level magnetic frustration and macroscopic elastic anisotropy, providing a consistent foundation for the thermomechanical design of alloys. • PBE + U framework reveals the electronic origin of FCC CoCrFeNi stability. • Cr exhibits local antiferromagnetic coupling to relieve magnetic frustration. • Directional d-d orbital hybridization creates a pseudogap at the Fermi level. • Band dispersion topology governs the pronounced 3D elastic anisotropy. • Bulk modulus from Birch-Murnaghan EOS matches elastic constants derivation.