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XVII.C.1.

Calculated Ionization Energy for C4 (Carbon tetramer)

Experimental Ionization Energy is 12.54 ± 0.35 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
semi-empirical AM1  
PM6  
composite G2 10.804
G3 10.907
G4 10.562
CBS-Q 10.913

Ionization Energies in eV
Methods with standard basis sets
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP cc-pVDZ cc-pVTZ aug-cc-pVDZ aug-cc-pVTZ
hartree fock HF 7.777 10.349 10.349 10.187 10.292 10.292 10.447 10.476 10.476 10.336 10.499 10.443 10.483 10.476  
density functional LSDA 9.063 11.148 11.148 10.919 10.943 10.943 11.156 11.218 11.218 10.992   11.111 11.232 11.165  
SVWN   11.851         11.852                
BLYP 8.758 10.802 10.802 10.634 10.654 10.654 10.909 10.916 10.916 10.708   10.832 10.946    
B1B95 9.094 11.157 11.157 11.010 10.944 11.044 10.419 11.244 11.244 11.082   11.190 11.150 11.127  
B3LYP 9.001 11.081 11.081 10.926 10.966 10.966 11.186 11.203 11.203 11.012 11.255 11.124 11.224 11.190 10.471
B3PW91 9.149 11.261 11.261 11.065 11.111 11.111 11.280 11.309 11.309 11.146   11.250 11.315    
mPW1PW91 9.133 11.259 11.259 11.064 11.114 11.114 11.287 11.303 11.303 11.147   11.250 11.315    
M06-2X         11.114                    
PBEPBE 9.476 11.388 11.388 11.218 11.283 11.283 11.516 11.484 11.484 11.305   11.441 11.489    
PBE1PBE         11.093                    
HSEh1PBE         11.083                    
TPSSh             11.159                
Moller Plesset perturbation MP2 7.638 10.318 10.318 10.146 10.519 10.519 10.749 10.812 10.812 10.784 10.808 10.752 11.010 10.873  
MP2=FULL 7.637 10.322 10.322 10.149 10.533 10.533 10.764 10.824 10.824 10.809   10.758 11.048    
MP3=FULL         10.482   10.697                
MP4   10.102     10.308       10.601       10.843    
B2PLYP         10.873               11.475    
Configuration interaction CID   10.222 10.222 10.016 10.426                    
CISD   10.231 10.231 10.020 10.425     10.684              
Quadratic configuration interaction QCISD   10.073 10.073 9.888 10.311 10.311 10.524 10.598 10.598 10.613   10.531 10.818    
QCISD(T)         10.248                    
Coupled Cluster CCD   10.054 10.054 9.865 10.311 10.311 10.523 10.598 10.598 10.613   10.541 10.819    

Ionization Energies in eV
Methods with effective core potentials (select basis sets)
CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD
hartree fock HF 10.205 10.317 10.275 10.434 10.310 10.309
density functional B3LYP 10.920 10.954 10.994 11.066 11.143 11.125
Moller Plesset perturbation MP2 10.270 10.567 10.360 10.725 10.443 10.445
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.