Study of Self-Interaction Errors in Density Functional Calculations of Magnetic Exchange Coupling Constants

It is well documented that self-interaction error (SIE) in density functional approximations (DFAs) is responsible for delocalization error resulting in a systematic error in the calculation of magnetic exchange coupling (J) constants. We investigate the role of SIE in DFAs belonging to the lowest three rungs of Jacob’s ladder of functionals, (namely, the local spin density approximation, Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA)and the recent SCAN family of meta-GGA functionals) on the evaluation of J coupling constants. To this end, we use three self-interaction correction (SIC) approaches that include the the Perdew-Zunger (PZSIC)¹ approach,orbital (OSIC)² and local scaling methods (LSIC)³.The molecular systems studied here are a benchmark set of H-He-H models, organic radicals, and hexa-chlorocuprates. Our results show that for the systems that mainly consist of single-electron regions, PZSIC performs well but for more complex organic systems and the chlorocuprates, an over-correcting tendency of PZSIC becomes more pronounced, and in such cases LSIC performs better than PZSIC. We find that both the density and energy corrections are crucial in order to improve the magnetic exchange coupling prediction.

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[2] O. A. Vydrov et al., J. Chem. Phys. 124, 094108 (2006).

[3] R. R. Zope, et al., J. Chem. Phys. 151, 214108 (2019).

[4] P. Mishra, et al., J. Phys. Chem. A 126.12 (2022)