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 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  
composite G2 11.649
G3 11.656
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) TZVP Def2TZVPP 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   14.624 10.004 10.011 10.012 10.004 10.011 10.011
density functional LSDA 10.895 12.381 12.381 12.172 12.102 12.105 12.266 12.346 12.343 12.127     12.218 12.341   12.274 12.347  
BLYP   11.451 11.451   12.333                          
B1B95 10.204 11.571 11.570 11.353 11.223 11.263 11.385 11.493 11.428 11.236     11.359 11.434   11.371 11.398  
B3LYP 10.175 11.612 11.612 11.405 11.349 11.348 11.541 11.540 11.539 11.303   14.589   11.533 11.556 11.527 11.575 11.559
B3LYPultrafine         11.349                       11.555  
B3PW91 10.204 11.640 11.640 11.398 11.330 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     14.535                              
PBEPBE   11.611 11.611   11.294 11.296 11.463 11.500 11.517 11.311     11.409 11.530        
PBE1PBE         11.248                          
HSEh1PBE   13.419     14.497                 13.725        
TPSSh                           14.583        
wB97X-D     14.520   14.363   14.484   14.493   14.494   14.484 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) TZVP Def2TZVPP 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 13.583 10.941 11.088 13.797 11.200 11.153   13.934 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) TZVP Def2TZVPP 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        
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     11.515  
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) TZVP Def2TZVPP 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)
daug-cc-pVDZ daug-cc-pVTZ daug-cc-pVQZ Sadlej_pVTZ CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD
hartree fock HF         10.039 9.850 10.151 9.976 10.205 10.207
density functional B3LYP         11.225 11.034 11.443 11.352 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.