Validation of density functionals for transition metals and intermetallics using data from quantitative electron...

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Chemistry

Background:

• Density functional theory (DFT) is crucial for predicting material properties.
• Accurate validation of DFT approximations is essential for reliable predictions.
• Experimental structure factors provide a rigorous benchmark for theoretical calculations.

Purpose of the Study:

• To validate various density functional theory (DFT) approximations using experimentally measured low-order structure factors (Fg).
• To assess the performance of different DFT functionals, including LDA, LDA + U, and GGA, for transition metals and intermetallic compounds.
• To explore the utility of low-order Fg as a metric for developing improved DFT functionals.

Main Methods:

• Quantitative convergent beam electron diffraction (QCBED) was employed to measure 23 low-order structure factors (Fg).
• Measurements were performed on transition metals (Cr, Fe, Co, Ni, Cu) and intermetallic phases (γ-TiAl, β-NiAl, γ1-FePd).
• Experimental Fg were compared with ab initio DFT calculations using LDA, LDA + U, and various GGA functionals.

Main Results:

• Different DFT functionals exhibited varying performance across different materials and crystal structures.
• GGA functionals generally agreed well with experimental Fg for BCC Cr and Fe, while EV93 excelled for FCC Ni and Cu.
• LDA and standard GGA functionals failed to accurately predict Fg for β-NiAl and γ1-FePd.
• The LDA + U approach, with optimized U values, achieved excellent agreement with experimental Fg for all investigated metallic systems.

Conclusions:

• Experimentally determined low-order structure factors serve as a valuable metric for validating DFT calculations.
• The LDA + U method demonstrates significant potential for accurate electronic structure calculations in metallic systems.
• This study highlights the need for improved DFT functionals and provides a pathway for their development.