Orbital Concept for Methane Activation
7
Table 2
Computed molecular orbital energies of methane from extended Hückel calculations and Hartree–Fock and DFT calculations with the 6-311++G**
basis set
Method
Molecular orbitals (eV)
HOMO–LUMO gap (eV)
Distance (Å)
1a
1
1t
2
2a
1
*
2t
2
*
Extended Hückel
−24.9
−15.6
37.0
4.9
20.4
1.091 a
Hartree–Fock/6-311++G**
−25.7
−14.9
1.1
2.1
16.0
1.084
DFT
SVWN/6-311++G**
−17.4
−9.9
−0.6
0.8
9.3
1.097
BLYP/6-311++G**
−16.9
−9.4
−0.4
0.9
8.9
1.097
PBE/6-311++G**
−17.0
−9.4
−0.3
1.0
9.1
1.098
B3LYP/6-311++G**
−19.0
−10.8
−0.2
1.1
10.6
1.091
PBE0/6-311++G**
−21.7
−12.4
0.5
1.6
13.0
1.088
M06/6-311++G**
−19.2
−11.0
−0.9
0.0
10.0
1.091
TPSSh/6-311++G**
−18.4
−10.2
0.0
1.2
10.2
1.092
a
Optimized by B3LYP