National Institute of Standards and Technology
Computational Chemistry Comparison and Benchmark DataBase
Release 22May 2022
NIST Standard Reference Database 101
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XVII.C.1. (III.D.6.)

Calculated Ionization Energy for C2H2O2 (Ethanedial)

Experimental Ionization Energy is 10.2 eV
Please note! These calculated ionizataion energies have the vibrational zero-point energy (zpe) included, but the zpe has NOT been scaled. Click on an entry for more details, including the ionization energy with a scaled zpe.
Original data displayed. Press to display differences.
Differences displayed. Press to display original data.

Ionization Energies in eV
Methods with predefined basis sets
composite G3B3 10.098

Ionization Energies in eV
Methods with standard basis sets
3-21G 3-21G* 6-31G* 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) 6-311+G(3df,2p) TZVP cc-pVDZ cc-pVTZ aug-cc-pVTZ daug-cc-pVTZ
hartree fock HF                 9.494       9.450
density functional BLYP     9.356                    
B3LYP                 9.970        
M06-2X   9.999 9.998         10.091          
PBE1PBE     9.854                    
HSEh1PBE 9.786   9.845 10.039             9.870    
TPSSh             9.524            
wB97X-D   9.850 9.939     9.919     9.990     9.957  
B97D3 9.421   9.508 9.732   9.532   9.633 9.638   9.560 9.629 9.627
3-21G 3-21G* 6-31G* 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) 6-311+G(3df,2p) TZVP cc-pVDZ cc-pVTZ aug-cc-pVTZ daug-cc-pVTZ
Moller Plesset perturbation MP2     9.931   9.749       9.911        
B2PLYP     9.694               9.819    
B2PLYP=FULLultrafine     9.695             9.624 9.826 9.909  
3-21G 3-21G* 6-31G* 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) 6-311+G(3df,2p) TZVP cc-pVDZ cc-pVTZ aug-cc-pVTZ daug-cc-pVTZ

Ionization Energies in eV
Methods with effective core potentials (select basis sets)
CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD cc-pVTZ-PP aug-cc-pVTZ-PP Def2TZVPP
hartree fock HF                 9.433
density functional B3LYP                 9.929
PBEPBE                 9.631
Moller Plesset perturbation MP2                 10.080
For descriptions of the methods (AM1, HF, MP2, ...) and basis sets (3-21G, 3-21G*, 6-31G, ...) see the glossary in section I.C. Predefined means the basis set used is determined by the method.