Error Decomposition in Dissociation Processes within Density-Corrected DFT: An Ensemble Perspective

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Density functional theory (DFT) is a cornerstone of electronic structure calculations.
• Standard DFT methods often exhibit delocalization and static correlation errors.
• These errors lead to inaccuracies in describing bond dissociation, particularly for simple molecular systems.

Purpose of the Study:

• To investigate the efficacy of density-corrected DFT (DC-DFT) in improving bond dissociation energetics.
• To understand the role of localized electron densities in mitigating DFT errors.
• To analyze the relationship between dissociation errors, fractional charge, and ensemble behavior within DC-DFT.

Main Methods:

• Application of DC-DFT to molecular systems including NaCl, H2+, He2+, and H2.
• Utilized both Hartree-Fock (HF) and alternative localized densities.
• Compared the performance of exact HF densities versus approximate localized densities within DC-DFT.

Main Results:

• DC-DFT with localized densities significantly improves dissociation energetics for systems like NaCl and H2+.
• Localized densities can yield more accurate energies than exact densities when used with approximate DFT functionals.
• Localization effectively compensates for functional errors by promoting integer charge behavior.

Conclusions:

• DC-DFT offers a viable route to correct bond dissociation errors inherent in standard DFT.
• The choice of electron density representation is crucial for accurate dissociation energy calculations.
• Understanding ensemble behavior is key to diagnosing and correcting DFT's limitations.