Table 3.

The Shannon ionic radii of six-fold coordinated Ni³⁺ and Fe³⁺ species in high and low-spin states, the Magules interaction parameters W from Eq. (4), and the Ni-O and Fe-O bond lengths derived assuming radius of oxygen of 1.38 Å, and computed here with the DFT+U(WF) method considering the average of the four shortest bond lengths (in parentheses)

	Ni3+	Fe3+	W0 (kJ/mol)	WFe (kJ/mol)	WNi (kJ/mol)	Ni-O (Å)	Fe-O (Å)	Ni-O (Å)9	Fe-O (Å)9
Low-spin	0.56	0.55	0.02	2.12	14.9	1.92 (1.92)	1.91 (1.90)	1.89 ± 0.02	1.91 ± 0.02
High-spin	0.60	0.65	2.82	4.92	17.52	1.96	2.01 (2.00)

Ionic radii data have been taken from ref. ⁵³. The last two columns report the Ni-O and Fe-O bond lengths measured with EXAFS spectroscopy for 25% Fe concentration in γ-NiOOH⁹.