National Institute of Standards and Technology
Computational Chemistry Comparison and Benchmark DataBase
Release 17bSeptember 2015
NIST Standard Reference Database 101
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XVII.C.1. (III.D.6.)

Calculated Ionization Energy for C2N2 (Cyanogen)

Experimental Ionization Energy is 13.37 ± 0.01 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  
PM3  
PM6  
composite G2 13.352
G3 13.361
G3B3 13.394
G4 13.403
CBS-Q 13.269

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 cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ
hartree fock HF 9.600 12.199 12.199 12.122 11.984 11.984 12.038 12.076 12.076 11.911 12.102 11.982 12.019   11.972 12.020 12.026
density functional LSDA 12.012 13.624 13.624 13.604 13.514 13.514 13.657 13.734 13.734 13.506   13.537 13.713   13.652 13.725  
SVWN   13.624         13.657       13.743            
BLYP 10.995 12.531 12.531 12.537 12.440 12.440 12.632 12.658 12.658 12.435   12.470 12.662        
B1B95 11.510 12.983 12.983 12.944 12.705 12.839 12.950 12.977 12.977 12.819   12.858 12.822   12.794 12.836  
B3LYP 11.422 12.952 12.952 12.942 12.835 12.835 12.984 13.024 13.024 12.819 13.059   13.015 13.037 12.977 13.032 13.039
B3LYPultrafine         12.835                     13.032  
B3PW91 11.538 13.094 13.094 13.024 12.917 12.917 13.016 13.061 13.061 12.885   12.932 13.033        
mPW1PW91 11.547 13.063 13.101 13.026 12.879 12.879 12.982 13.015 13.050 12.879   12.893 12.991        
M06-2X     13.232   13.232                        
PBEPBE 11.240 12.791 12.791 12.751 12.652 12.652 12.801 12.820 12.820 12.632   12.675 12.819        
PBE1PBE         12.892                        
HSEh1PBE   13.052     12.874   12.980           12.999        
TPSSh         12.705   12.809     12.667     12.827        
wB97X-D     13.204   13.004       13.141       13.089     13.099  
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 cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ
Moller Plesset perturbation MP2 12.628 13.876 13.876 14.023 14.091 14.091 14.223 14.247 14.247 14.284 14.247 14.172     14.356    
MP2=FULL 12.628 13.877 13.877 14.025 14.095 14.095 14.227 14.256 14.256 14.294   14.176          
MP3         13.214                        
MP3=FULL         13.222   13.317                    
MP4   13.267     13.480       13.669                
B2PLYP         13.027               13.248        
Configuration interaction CID   12.976 12.976 13.025 13.010     13.147                  
CISD   12.851 12.851 12.873 12.906     13.044                  
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 cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ
Quadratic configuration interaction QCISD       12.767 12.843 12.843 12.940 12.982 12.982     12.880          
QCISD(T)         12.842             12.885     13.034    
Coupled Cluster CCD   13.234 13.234 13.338 13.343 13.343 13.442 13.482 13.482     13.396     13.532    
CCSD         12.897                        
CCSD(T)                       12.928     13.079    
CCSD(T)=FULL         12.897                        
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 cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ

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 12.153 11.913 12.132 12.039 12.152 12.151
density functional B3LYP 12.953 12.755 12.930 12.849 13.047 13.030
Moller Plesset perturbation MP2 14.181 14.145 14.196 14.195 14.226 14.229
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.