Variational, Self-Consistent Implementation of the Perdew-Zunger Self-Interaction Correction with Complex Optimal...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Self-interaction error is a significant limitation in standard density functional theory (DFT) approximations.
• This error affects the accuracy of calculated properties, particularly for systems with localized electrons.
• Perdew-Zunger Self-Interaction Correction (PZ-SIC) offers a way to mitigate this error.

Purpose of the Study:

• To develop and present a variational, self-consistent implementation of PZ-SIC for finite systems using atom-centered basis sets.
• To introduce a simplifying approximation for using real canonical orbitals.
• To assess the performance of the implemented PZ-SIC with various generalized gradient and meta-generalized gradient functionals.

Main Methods:

• A unified Hamiltonian and complex optimal orbitals form the basis of the PZ-SIC implementation.
• A two-step self-consistent field (SCF) iteration algorithm is employed, updating canonical and optimal orbitals separately.
• Calculations were performed for atoms (H to Ar) and the CH3 + F(-) complex using PBE, APBE, PBEsol, and TPSS functionals.

Main Results:

• The PZ-SIC significantly improves the accuracy of atomic energies, bringing them into agreement with high-level ab initio calculations, especially for functionals like PBEsol.
• The use of complex optimal orbitals is crucial for accurate results with meta-generalized gradient functionals like TPSS.
• The method successfully addresses the charge localization problem, yielding accurate energy and charge estimates for the CH3 + F(-) complex, comparable to coupled cluster results.

Conclusions:

• The presented variational PZ-SIC implementation is effective for finite systems and improves the accuracy of commonly used DFT functionals.
• The distinction between real and complex optimal orbitals is critical for certain functionals and systems.
• This approach offers a robust way to handle self-interaction errors and charge localization in electronic structure calculations.