Imagine a material made by mixing five different metal elements equally—magnesium, copper, nickel, cobalt, and zinc. Because of this mix, each oxygen atom in the material “sees” a different neighborhood of metal atoms around it. This complex mixture is called a high entropy oxide (HEO).
Now, oxygen atoms can sometimes leave their spots and create “holes” or vacancies, which are missing oxygen atoms in the crystal structure. These vacancies aren’t just flaws—they can strongly affect how the material behaves, especially in electronics, energy storage, or catalysis.
In their study, MSE PhD Student Oriyomi Opetubo et al. used both computer modeling (density functional theory) and physical experiments to find out how easy or hard it is for oxygen to leave its spot (called the “vacancy formation energy,” or EvfE_vfEvf) SSRN. They discovered:
- The different metals around the oxygen atom cause a wide range of EvfE_vfEvf values—some spots lose oxygen more easily than others. SSRN+1
- Having copper in the mix lowers EvfE_vfEvf, meaning more oxygen vacancies tend to form when copper is present. SSRN
- The metal atoms distort the crystal—some stretch or squeeze the lattice. These distortions affect how big the vacancy “hole” is, and bigger holes tend to require more energy to form. SSRN+1
- How metals charge and their electronegativity (a measure of how strongly an atom attracts electrons) also matters: metals that pull electrons more can stabilize vacancies more easily. SSRN
By linking the mix of elements, charges, and distortions, the authors create a clearer picture of what controls vacancy formation in these “disordered” materials. This knowledge can help scientists design better oxides for batteries, catalysts, and other devices, by tuning how many vacancies there are and where they form.
To read this article click here
Opetubo, O.; Shen, T.; Bordia, R.; Aidhy, D. S. Fundamental understanding of oxygen vacancy energetics in rocksalt Mg (CuNiCoZn)O high entropy oxide from DFT and experiments. ACTA MATERIALIA 2025, 296.
