Ionization potentials and electron affinities in the Perdew-Zunger self-interaction corrected density-functional...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Density-functional theory (DFT) is a powerful tool for electronic structure calculations.
• Self-interaction error (SIE) is a known limitation in standard DFT approximations.
• Self-interaction correction (SIC) methods aim to mitigate SIE.

Purpose of the Study:

• To evaluate the performance of the Perdew-Zunger self-interaction corrected (PZ-SIC) method for calculating ionization potentials (IP) and electron affinities (EA).
• To compare PZ-SIC performance with various exchange-correlation functionals and calculation methods.
• To assess PZ-SIC accuracy for both atoms and molecules.

Main Methods:

• Self-consistent implementation of the Perdew-Zunger self-interaction corrected (PZ-SIC) density-functional theory.
• Calculation of IPs and EAs for first- and second-row atoms and small molecules.
• Two methods for IP/EA determination: delta self-consistent field (delta-SCF) and negative of highest-occupied orbital energies.

Main Results:

• PZ-SIC generally worsens delta-SCF calculated IPs and EAs, except for the local spin-density approximation.
• PZ-SIC significantly improves the agreement between orbital eigenvalues and electron removal energies.
• PZ-SIC shows diminished performance for molecules compared to atoms, suggesting over-correction in many-electron systems.

Conclusions:

• PZ-SIC offers benefits for orbital energy calculations but presents challenges for direct IP/EA predictions via delta-SCF.
• The effectiveness of PZ-SIC varies between atoms and molecules.
• Further investigation into PZ-SIC approximations, like spherical averaging, is warranted.