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)

From: Low-spin state of Fe in Fe-doped NiOOH electrocatalysts

 

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)

  
  1. 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.
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