National Institute of Standards and Technology
Computational Chemistry Comparison and Benchmark DataBase
Release 19April 2018
NIST Standard Reference Database 101
IIntroduction
IIExperimental data
IIICalculated data
IVData comparisons
VCost comparisons
VIInput and output files
VIITutorials and Units
VIIILinks to other sites
IXFeedback
XOlder CCCBDB versions
XIIGeometries
XIII Vibrations
XIVReaction data
XVEntropy data
XVIBibliographic data
XVIIIon data
XVIIIBad calculations
XIXIndex of properties
XXH-bond dimers
XXIOddities

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XVII.C.1. (III.D.6.)

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
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 Def2TZVPP 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 10.498 10.443 10.483 10.476  
density functional BLYP 8.758 10.802 10.802                   10.832      
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    
B3LYP 9.001 11.081 11.081 10.926 10.966 10.966 11.186 11.203 11.203 11.012 11.255 11.243 11.124 11.224   10.471
B3LYPultrafine                               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     11.174   11.114                      
PBEPBE 9.476 11.388 11.388 11.218 11.283 11.283 11.516 11.484 11.484 11.305   11.500 11.441 11.489    
PBE1PBE         11.093                      
HSEh1PBE   11.220     11.083   11.262             11.298    
TPSSh         10.991   11.159     11.022       11.194    
wB97X-D     11.186   11.039   11.217   11.244   11.277   11.217 11.239   11.255
B97D3   11.026                       10.987    
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP Def2TZVPP cc-pVDZ cc-pVTZ aug-cc-pVDZ aug-cc-pVTZ
Moller Plesset perturbation MP2 7.638 10.318 10.318   10.519 10.519 10.749 10.812 10.812 10.784   11.040 10.752 11.010    
MP2=FULL 7.637 10.322 10.322   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                      
Configuration interaction CID   10.222 10.222   10.426                      
CISD   10.231 10.231   10.425     10.684                
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP Def2TZVPP cc-pVDZ cc-pVTZ aug-cc-pVDZ aug-cc-pVTZ
Quadratic configuration interaction QCISD   10.073 10.073   10.311 10.311 10.524 10.598 10.598 10.613     10.531 10.818    
Coupled Cluster CCD   10.054 10.054   10.311 10.311 10.523 10.598 10.598 10.613     10.541 10.819    
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP Def2TZVPP cc-pVDZ cc-pVTZ aug-cc-pVDZ aug-cc-pVTZ

Ionization Energies in eV
Methods with effective core potentials (select basis sets)
daug-cc-pVDZ daug-cc-pVTZ daug-cc-pVQZ Sadlej_pVTZ 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           10.567   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.