First-principles study of oxide formation and stability in the equiatomic CoCrFeNi high-entropy alloy

Abstract

Atomistic modeling using first-principles density functional theory was employed to investigate the early-stage oxidation and passivity of CoCrFeNi high-entropy alloy (HEA). Our findings reveal increased adsorption energy and charge transfer for sites with higher Cr density, indicating preferential Cr oxidation. The work function of the HEA increases with adsorbate coverage due to changes in the electrostatic dipole moment between HEA and adsorbates. Diffusion activation energies showed no correlation with local atomic configurations but were accurately predicted using an effective spatial-energy parameter. Density of states and d-band center calculations indicated a shift toward the Fermi level, suggesting enhanced surface reactivity, particularly for Cr. The HEA surface demonstrated high oxygen reactivity at high temperatures and low pressures, making recovery of the clean surface impossible. These insights facilitated the calculation of the oxygen diffusion coefficient, advancing the understanding of oxide formation and stability in CoCrFeNi HEA.