18 / 2025-02-24 21:54:12

Complex band structure of the high-entropy oxide (MgCoNiCuZn)O accounting for its drastic decrease in the electrical resistance at high pressure

high entropy,oxide,Electrical conductivity,high pressure,bandgap,density functional theory,Band structure

Previous studies showed that the electrical resistance of the high-entropy oxide (HEO) (MgCoNiCuZn)O markedly decreases as pressure increases up to around 40 GPa, which is beyond what is expected based on the slight reduction in the optical bandgap determined from the UV-Vis measurements [1]. To circumvent the limitations in the UV-Vis measurements of the bandgaps, density-functional theory (DFT) calculations were employed to determine the electronic density of states (DOS) of the HEO at various pressures. The calculations revealed a complex band structure of the HEO under high pressure, exhibiting spin-up bandgaps, spin-down bandgaps, spin-down intermediate gaps, and secondary excitation gaps. Some of these gaps fall outside the energy range detectable by the UV-Vis experiments. However, they do play a role in the electrical conductance of the HEO. In particular, certain bandgaps are closed at high pressure, which significantly impacts the electrical conductance. Our DFT calculations provides new insights into the electronic structure – property relationship not directly inferable from the experimental measurements.