Advancing DFT predictions in Cu-chalcogenides with full-yet-shallow 3d-orbitals: Meta-GGA plus Hubbard-like U...

Area of Science:

• Materials Science
• Computational Chemistry
• Condensed Matter Physics

Background:

• Copper chalcogenides (Cu2Se, CuInSe2) are technologically important but challenging to model due to Cu-3d orbitals.
• Conventional density functional theory (DFT) functionals struggle with accurate electronic property descriptions.

Purpose of the Study:

• Evaluate recently developed meta-generalized gradient approximation (meta-GGA) functionals for Cu-chalcogenides.
• Improve the accuracy of electronic structure calculations for these materials.

Main Methods:

• Applied several meta-GGA functionals, including r2SCAN, to Cu-chalcogenides.
• Investigated the effect of Hubbard U correction on Cu-3d orbitals.
• Compared results with experimental data, hybrid functionals, and GW approximation.

Main Results:

• r2SCAN functional improved geometry and band structure over conventional GGA but showed delocalization error.
• Combining r2SCAN with U correction (r2SCAN+U) mitigated delocalization error.
• TASK and mBJ+U showed good band gap prediction accuracy, comparable to each other but less than GW.
• r2SCAN+U accurately reproduced phonon dispersion in CuInSe2.

Conclusions:

• Meta-GGA+U approach offers a good balance between reliability and computational cost for Cu-chalcogenides.
• Further work is needed for more precise Cu-3d orbital descriptions.
• r2SCAN+U addresses previously overlooked computational issues in CuInSe2 phonon calculations.