Table 2.

Occupations of d orbitals computed with the DFT and DFT+U approaches, with the atomic orbitals as projectors, and with the DFT+U(WF) approach that uses a Wannier functions-based representation as projectors of the d orbitals

	β-Ni(OH)2	β-NiOOH	Fe-doped β-NiOOH
	Ni2+	Ni3+	${\mathrm{Fe}}_{\mathrm{HS}}^{3+}$	${\mathrm{Fe}}_{\mathrm{LS}}^{3+}$
DFT	8.4	8.6	6.3	7.0
DFT+U	8.4	8.5	6.2	6.6
DFT+U(WF)	8.0	6.9	4.8	5.0
Expected	8.0	7.0	5.0	5.0