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Calculated Ionization Energy for C4H2 (Diacetylene)

20 09 09 14 00
Experimental Ionization Energy is 10.17 ± 0.02 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 G2 10.157
G3 10.132
G3B3 10.210
G4 -454187.631
CBS-Q 10.263

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                 8.846       8.804
density functional BLYP     9.272                    
B3LYP                 9.844        
B3LYPultrafine                       9.838  
M06-2X   10.091 9.840                    
PBEPBE               9.755          
PBE1PBE     9.610                    
HSEh1PBE 9.882   9.590 9.752             9.803    
TPSSh     9.469 9.630     9.481     9.581 9.683    
wB97X-D   9.976 9.661 9.821   9.889     9.884 9.821 9.858 9.864  
B97D3 9.666   9.388 9.576   9.618   9.640 9.644   9.615 9.630  
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     10.147   10.393       10.410        
MP3=FULL     9.699 9.880                  
B2PLYP     9.636               9.961    
Coupled Cluster CCSD(T)=FULL     9.625                    
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                 8.807
density functional B3LYP                 9.832
PBEPBE                 9.740
Moller Plesset perturbation MP2                 10.634
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.