Source-Free Exchange-Correlation Magnetic Fields in Density Functional Theory

Area of Science:

• Condensed Matter Physics
• Quantum Chemistry
• Materials Science

Background:

• Spin-dependent exchange-correlation energy functionals are crucial in density functional theory (DFT).
• Current functionals depend on charge and magnetization densities (E_xc[ρ, m]).
• An alternative formulation using the curl of magnetization density (E_xc[ρ,∇ × m]) can yield a source-free exchange-correlation magnetic field (B_xc).

Purpose of the Study:

• To investigate the impact of a source-free formulation of exchange-correlation functionals.
• To remove the source term from local and generalized gradient approximations.
• To evaluate the improvement in predicting magnetic properties.

Main Methods:

• Reformulating spin-dependent exchange-correlation energy functionals using the curl of magnetization density.
• Applying this source-free approach to local and generalized gradient approximations.
• Comparing calculated Kohn-Sham magnetic moments with experimental data.

Main Results:

• The source-free method successfully removes the source term from B_xc.
• Total Kohn-Sham magnetic moments are improved for a broad range of materials.
• Predictions for pnictides show significantly better agreement with experimental values.

Conclusions:

• The source-free formulation offers a simple yet effective way to enhance magnetic property predictions in DFT.
• This method is readily implementable in existing DFT codes.
• It provides a valuable tool for accurate materials modeling, particularly for magnetic materials.