A linear-response approach for first-principles Hund's J parameters: insights, oxides, and self-consistency*

Hubbard U parameters quantify the many-electron self-interaction error associated with selected subspaces in approximate DFT. We describe the interpretation and calculation of its lesser-known counterpart, Hund's J, as a measure instead of subspace static correlation error. We show how Hund's J can be readily calculated like the Hubbard U using minimum-tracking [1] (constrained DFT based [2]) linear-response, sometimes as a cost-free by-product [3]. We demonstrate that J-moderated DFT+U yields rather satisfactory results for several oxides including MnO [3], TiO2 (rutile and anatase) [4], Cr2O3, and NiO [1]. We revise the parameter self-consistency condition in light of new results on the role of Hund's J [1].

[1] G. Moynihan, Ph.D. thesis, Trinity College Dublin (2018) http://hdl.handle.net/2262/82220
[2] D. D. O’Regan and G. Teobaldi, Phys. Rev. B 94, 035159 (2016).
[3] E. B. Linscott, D. J. Cole, M. C. Payne and D. D. O’Regan, Phys. Rev. B 98, 235157 (2018).
[4] O. K. Orhan and D. D. O'Regan, Phys. Rev. B 101, 245137 (2020).