Table 2. Comparison of calculated electron affinities, LUMO energies and the next unoccupied virtual states for selected functionals. The ordering of the methods is subjective and reflects how well each approach reproduces (i) strong LUMO binding and (ii) the expected intensity ratio between the proposed LUMO and the (degenerate) LUMO+1 orbitals, which should follow a 1 : 2 ratio based on the derived frontier orbital model.

Method	ΔSCF electron affinity eqn (11) (eV)	LUMO (eV)	Next LUMO in DOS (eV)	Intensity ratio in DOS
M08-HX	0.3	−1.4	−1.0	1 : 2
M08-SO	0.25	−1.3	−0.9	1 : 2
B3LYP	0.2	−1.4	−0.9	1 : 2
LDA0 and PBE0	0.1–0.2	−1.25	−0.82	1 : 2
M11-L	0.4	−2.65	−2.3	1 : 2 : 2
M06	−0.1	−1.8	−1.45	1 : 3
TPSS	0.1	−2.1	−1.7	1 : 1
SCAN and R2SCAN	0.1	−2.0	−1.5	1 : 1
M06-L	−0.2	−1.9	−1.45	1 : 1
M11	0.0	−0.9	−0.5	1 : 2
PBE1/3	0.1	−0.85	−0.45	1 : 2
revM06	−0.15	−0.6	−0.2	1 : 2
LRC-PBE0*	1.8	−1.4	−0.8	1 : 2
M06-2X	−0.05	−0.8	−0.4	1 : 2 : 2
CAM-LDA0	0.7	−1.6	−1.1	1 : 1
TPSS0	NA	−1.05	−0.55	1 : 1
revM11	0.1	−0.1	0.3	1 : 2
LC-BLYP*	−0.1	0.07	0.45	1 : 2
LC-BLYP-EA	−0.1	0.07	0.42	1 : 2
LC-PBEOP	−0.15	0.25	0.65	1 : 2
PBE50	0.0	−0.25	0.15	2 : 3
CAM-PBE50*	0.6	−0.35	0.15	2 : 3
PBE-2X	0.0	−0.25	0.2	2 : 3
ωB97X-V	−0.1	0.3	0.65	1 : 2