Effect of ensemble generalization on the highest-occupied Kohn-Sham eigenvalue.

Area of Science:

• Quantum Chemistry
• Computational Materials Science
• Electronic Structure Theory

Background:

• Density-functional theory (DFT) approximations accurately predict total energy properties but struggle with potential-related processes like ionization potentials.
• Developing a single exchange-correlation functional for both energy and potential properties remains a significant challenge in electronic structure theory.

Purpose of the Study:

• To investigate the efficacy of the ensemble generalization procedure for improving ionization potential predictions in DFT.
• To assess whether ensemble generalization compromises the accuracy of total energy-related properties.

Main Methods:

• Applied the ensemble generalization procedure to various exchange-correlation functionals, including local spin-density approximation, generalized gradient approximations, and hybrid functionals.
• Evaluated predictions for ionization potentials using the highest occupied Kohn-Sham eigenvalue on a test set of 26 diatomic molecules and single atoms.

Main Results:

• The ensemble generalization systematically improved ionization potential predictions across different functionals and systems.
• Accuracy of total energy-related properties was maintained after applying ensemble generalization.
• Ensemble-generalized hybrid functionals showed weak dependence on the parameter controlling semi-local and non-local components, mitigating the 'parameter dilemma'.

Conclusions:

• Ensemble generalization is a promising approach to simultaneously improve potential-related properties and maintain accuracy for energy-related properties in DFT.
• This method offers a potential solution to the long-standing challenge of developing versatile exchange-correlation functionals.