Table 1 The band gaps of β-Ni(OH)₂ and β-NiOOH calculated with different exchange-correlation functionals

This work

 DFT

1.66/0.60

2.77/0.00

 DFT + U

2.60/2.55

2.61/0.00

 DFT + U(WF)

3.72/3.42

3.89/3.55

 HSE06

3.45/3.40

2.78/1.1

Previous results

 exp.

3.6–3.9^a

1.7–3.75^a,b,c

 DFT

0.95–2.90^d,e

0.01–0.04^f

 DFT + U

–/2.98^g

0.00–0.19^f,g,h

 PBE0

3.17/3.17ⁱ

 PBE0α

1.00–2.75^*,f,h,i,j

 HSE06

4.2^k

0–1.73^f,h,k