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Abstract Entropic stabilization has evolved into a strategy to create new oxide materials and realize novel functional properties engineered through the alloy composition. Achieving an atomistic understanding of these properties to enable their design, however, has been challenging due to the local compositional and structural disorder that underlies their fundamental structure-property relationships. Here, we combine high-throughput atomistic calculations and linear regression algorithms to investigate the role of local configurational and structural disorder on the thermodynamics of vacancy formation in (MgCoNiCuZn)O-based entropy-stabilized oxides (ESOs) and their influence on the electrical properties. We find that the cation-vacancy formation energies decrease with increasing local tensile strain caused by the deviation of the bond lengths in ESOs from the equilibrium bond length in the binary oxides. The oxygen-vacancy formation strongly depends on structural distortions associated with the local configuration of chemical species. Vacancies in ESOs exhibit deep thermodynamic transition levels that inhibit electrical conduction. By applying the charge-neutrality condition, we determine that the equilibrium concentrations of both oxygen and cation vacancies increase with increasing Cu mole fraction. Our results demonstrate that tuning the local chemistry and associated structural distortions by varying alloy composition acts an engineering principle that enables controlled defect formation in multi-component alloys.
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The thermodynamic effects of solute on void nucleation in Mg alloys
Replica exchange transition interface sampling simulations in Mg–Al alloys with high vacancy concentrations indicate that the presence of a solute reduces thermodynamic barriers to the clustering of vacancies and the formation of voids. The emergence of local minima in the free energy along the reaction coordinate suggests that void formation may become a multi-step process in the presence of a solute. In this scenario, vacancies agglomerate with solute before they coalesce into a stable void with well-defined internal surfaces. The emergence of vacancy–solute clusters as intermediate states would imply that classical nucleation theory is unlikely to adequately describe void formation in alloys at high vacancy concentrations, a likely precursor for alloy strengthening through nanoscale precipitation.
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- Award ID(s):
- 2320355
- PAR ID:
- 10528622
- Publisher / Repository:
- AIP
- Date Published:
- Journal Name:
- The Journal of Chemical Physics
- Volume:
- 161
- Issue:
- 4
- ISSN:
- 0021-9606
- Page Range / eLocation ID:
- 044509
- Subject(s) / Keyword(s):
- Free energy landscapes, Molecular dynamics, Monte Carlo methods, Potential energy surfaces, Metallurgy, Crystallographic defects, Alloys, Reaction rate constants
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1063/5.0196513
