Improved description of hematite surfaces by the SCAN functional.

Area of Science:

• Computational Materials Science
• Surface Science
• Solid-State Physics

Background:

• Surface termination of α-Fe2O3 (0001) is debated, depending on oxygen chemical potential.
• Standard Density Functional Theory (DFT) methods like PBE and PBE+U have limitations for hematite, causing errors in bandgap and failing to predict stable surfaces.

Purpose of the Study:

• To investigate the efficacy of the Strongly Constrained and Appropriately Normed (SCAN) approximation for DFT studies of hematite (α-Fe2O3) surfaces.
• To compare SCAN with PBE and PBE+U for describing α-Fe2O3 (0001) surface properties and electronic structure.

Main Methods:

• Density Functional Theory (DFT) calculations were performed.
• The performance of Perdew-Burke-Ernzerhof (PBE), PBE+U, SCAN, and SCAN+U functionals were compared.
• Calculations focused on the electronic structure, bandgap, lattice constants, and density of states for various α-Fe2O3 (0001) surface terminations.

Main Results:

• SCAN and SCAN+U functionals provide improved descriptions of the electronic structure for stoichiometric α-Fe2O3 (0001) surfaces compared to PBE.
• SCAN-based methods yield consistent predictions for surface terminations, aligning better with experimental synthesis.
• Bulk properties, including lattice constants and density of states, are also enhanced using the SCAN functional.

Conclusions:

• The SCAN approximation offers a more accurate approach for DFT studies of hematite systems, particularly for surface properties.
• SCAN and SCAN+U resolve limitations of PBE and PBE+U, enabling reliable characterization of α-Fe2O3 (0001) surfaces and their stoichiometry.