National Institute of Standards and Technology
Computational Chemistry Comparison and Benchmark DataBase
Release 17bSeptember 2015
NIST Standard Reference Database 101
IIntroduction
IIExperimental data
IIICalculated data
IVData comparisons
VCost comparisons
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XOlder CCCBDB versions
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XIII Vibrations
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XVEntropy data
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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 C4H2 (Diacetylene)

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
semi-empirical PM6  
composite G4 10.205

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) TZVP cc-pVTZ aug-cc-pVTZ
hartree fock HF               8.846    
density functional SVWN 10.485   10.244 10.434       10.528    
BLYP     9.272              
B3LYP               9.844    
B3LYPultrafine                   9.838
M06-2X   -13.091 9.840              
PBE1PBE     9.610              
HSEh1PBE 9.882   9.590 9.752         9.803  
TPSSh     9.469 9.630     9.481   9.683  
wB97X-D   9.976 9.661     9.889     9.858 9.864
3-21G 3-21G* 6-31G* 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP cc-pVTZ aug-cc-pVTZ
Moller Plesset perturbation MP2     10.147   10.469     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) TZVP cc-pVTZ aug-cc-pVTZ
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.