When Density Functional Approximations Meet Iron Oxides.

Area of Science:

• Materials Science
• Computational Chemistry
• Solid State Physics

Background:

• Iron oxides exhibit diverse properties crucial for various applications.
• Accurate theoretical prediction of iron oxide properties is essential for materials design.
• Previous density functional approximations (DFAs) have limitations in describing these properties.

Purpose of the Study:

• To evaluate three DFAs (PBE, PBE+U, HSE) for iron oxide properties.
• To identify the most reliable functional for predicting geometric, electronic, magnetic, and thermodynamic properties.
• To construct phase diagrams for iron oxide transformations.

Main Methods:

• Employed PBE, PBE+U, and HSE (a=0.15, a=0.25) functionals for calculations.
• Investigated geometric, electronic, magnetic, and thermodynamic properties of α-FeOOH, α-Fe2O3, Fe3O4, and FeO.
• Calculated Gibbs free energies and plotted equilibrium phase diagrams.

Main Results:

• HSE (a=0.15) accurately predicted lattice constants, magnetic moments, band gaps, and formation energies.
• Standard HSE (a=0.25) overestimated band gaps and formation energies.
• PBE+U required specific U values for electronic properties, lacking universal accuracy.
• Calculated phase diagrams offer insights into iron oxide transformations.

Conclusions:

• HSE (a=0.15) is a reliable functional for iron oxide property prediction.
• The study provides a theoretical basis for understanding iron oxide phase stability and transformations.
• Accurate computational methods are vital for advancing iron oxide research.