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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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 C2H (Ethynyl radical)

Experimental Ionization Energy is 11.61 ± 0.07 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 11.649
G3 11.656
G3B3 11.799
G4 11.809
CBS-Q 11.689

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) cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ
hartree fock HF 8.640 10.327 10.327 10.107 9.931 9.927 9.997 10.042 10.044 9.880 10.004 10.011 10.012 10.004 10.011 10.011
density functional LSDA 10.895 12.381 12.381 12.172 12.156 12.110 12.270 12.346 12.343 12.128 12.222 12.341   12.281 12.347  
SVWN   14.857         14.916                  
BLYP 9.993 11.452 11.452 11.250 12.511 11.193 11.395 11.414 11.422 11.208 11.318 11.445        
B1B95 10.204 11.571 11.570 11.353 11.223 11.263 11.422 11.493 11.428 11.266 11.359 11.434   11.407 11.398  
B3LYP 10.175 11.612 11.612 11.405 11.354 11.348 11.546 11.540 11.539 11.303   11.533 11.556 11.538 11.575 11.559
B3LYPultrafine         11.354                   11.555  
B3PW91 10.204 11.640 11.640 11.398 11.317 11.296 11.428 11.474 11.477 11.300 11.395 11.472        
mPW1PW91 10.159 11.580 11.602 11.357 11.229 11.221 11.362 11.394 11.419 11.244 11.320 11.397        
M06-2X     14.390                          
PBEPBE 10.151 11.611 11.611 11.439 11.320 11.321 11.488 11.508 11.520 11.329 11.433 11.534        
PBE1PBE         11.248                      
HSEh1PBE   13.419     14.497             13.725        
TPSSh         14.504   14.622     12.805   14.583        
wB97X-D     14.520   14.363       14.493     14.471     14.478  
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ
Moller Plesset perturbation MP2 9.102 10.973 10.973 10.747 10.900 10.941 11.088 11.147 11.200 11.153 11.086 11.388   11.188 11.425 11.494
MP2=FULL 9.103 10.976 10.976 10.750 10.934 10.957 11.104 11.183 11.217 11.181 11.097 11.430     11.469 11.532
MP3         10.799                      
MP3=FULL         13.741   13.905                  
MP4   10.990     10.918       11.197     13.855        
B2PLYP                       14.408        
Configuration interaction CID   10.846 10.846 10.622 10.695     10.903                
CISD   10.899 10.899 10.675 10.737     10.935                
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ
Quadratic configuration interaction QCISD   11.117 11.117 10.909 10.987 11.009 11.129 11.188 11.215 11.190 11.141 11.372        
QCISD(T)         11.062           11.223 11.500   11.325    
Coupled Cluster CCD     10.936 10.715 10.814 10.835 10.966 11.034 11.064 11.024 10.969 11.229   11.060 11.259  
CCSD(T)         11.055           11.223 11.483   11.354 11.515  
CCSD(T)=FULL         11.071                      
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) 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 10.039 9.850 10.151 9.976 10.205 10.207
density functional B3LYP 11.225 11.034 11.434 11.392 11.552 11.532
Moller Plesset perturbation MP2 10.559 10.748 10.812 11.009 10.865 10.871
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.