Reworking the Tao-Mo exchange-correlation functional. II. De-orbitalization

Area of Science:

• Quantum Chemistry
• Computational Materials Science
• Density Functional Theory

Background:

• The Tao-Mo exchange functional, while effective, suffers from an order-of-limits problem and unphysical behavior.
• Previous regularization efforts improved the functional but introduced complexities.
• De-orbitalization aims to convert orbital-dependent functionals into pure density functionals.

Purpose of the Study:

• To de-orbitalize the simplified, regularized Tao-Mo (sregTM) exchange functional into a pure density functional.
• To analyze the failures of the Mejía-Rodríguez and Trickey de-orbitalization strategy.
• To develop and evaluate a more accurate de-orbitalization method for the sregTM functional.

Main Methods:

• Regularization of the Tao-Mo exchange functional to create the sregTM version.
• Application and analysis of the Mejía-Rodríguez and Trickey de-orbitalization strategy.
• Development and testing of a modified de-orbitalization approach with peculiar parameterization.

Main Results:

• The sregTM functional maintains performance comparable to previous regularized versions.
• The Mejía-Rodríguez and Trickey strategy exhibits significant failures when applied to the sregTM functional and its predecessors.
• A modified de-orbitalization method shows partial success but is not recommended due to error cancellation.
• The study highlights the difficulty in correcting errors introduced by de-orbitalization in complex functionals.

Conclusions:

• The de-orbitalization of the sregTM functional presents significant challenges.
• The Mejía-Rodríguez and Trickey de-orbitalization approach is problematic for complex, two-indicator functionals.
• Careful parameterization and analysis are crucial for developing reliable pure density functionals from orbital-dependent ones.