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 S2 (Sulfur diatomic)

Experimental Ionization Energy is 9.356 ± 0.002 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 9.288
G3 9.389
G4 9.349
CBS-Q 9.434

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 cc-pV(D+d)Z cc-pV(T+d)Z aug-cc-pV(T+d)Z
hartree fock HF 6.590 10.434 9.478 10.331 9.466 9.466 9.454 9.410 9.410 9.278 9.377 9.391 9.274 9.251 9.407 9.288 9.256 9.306 9.231 9.245
density functional LSDA 6.914 3.381 10.054 10.503 10.038 10.038 10.051 10.024 10.024 9.925   9.992 9.956   10.032          
SVWN   10.614         10.051       10.020                  
BLYP 6.241 9.893 9.348 9.809 9.362 9.362 9.399 9.383 9.384 9.253   9.292 9.282              
B1B95 6.717 3.466 9.580 10.125 9.540 9.556 9.563 9.534 9.534 9.427   9.512 9.418 9.414 9.530 9.443 9.420   9.433 9.445
B3LYP 6.686 10.310 9.678 10.215 9.681 9.681 9.700 9.674 9.674 9.552 9.649 9.616 9.571 9.554 9.665 9.583 9.560   9.539 9.552
B3LYPultrafine         9.681                     9.584        
B3PW91 6.818 10.425 9.782 10.288 9.746 9.746 9.745 9.714 9.714 9.615   9.712 9.624              
mPW1PW91 6.854 10.429 9.795 10.326 9.733 9.733 9.734 9.708 9.737 9.628   9.694 9.607              
M06-2X     9.706   9.706                              
PBEPBE 6.443 10.105 9.545 9.995 9.537 9.537 9.555 9.541 9.541 9.427   9.485 9.444           9.417  
PBE1PBE         9.738                              
HSEh1PBE   9.315     9.681   9.683           9.558              
TPSSh         9.675   9.676     9.549     9.561              
wB97X-D     9.763   9.729       9.684       9.584     9.588        
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 cc-pV(D+d)Z cc-pV(T+d)Z aug-cc-pV(T+d)Z
Moller Plesset perturbation MP2 4.620   8.948 8.881 8.931 8.930 8.931 8.911 8.911 9.202 8.964 9.025 9.220 9.280 9.196 9.274 9.303   9.204 9.259
MP2=FULL         8.920 8.920 8.920 8.904 8.904     9.018 9.206 9.269       8.987 9.189 9.239
MP3         9.072                              
MP3=FULL         9.063   9.061                          
MP4         8.906               9.193              
B2PLYP         9.358               9.382              
Configuration interaction CID         9.137     9.106                        
CISD         9.126                              
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 cc-pV(D+d)Z cc-pV(T+d)Z aug-cc-pV(T+d)Z
Quadratic configuration interaction QCISD   9.506     9.028 9.028 9.030 9.007 9.008     9.110 9.342           9.316  
QCISD(T)         8.938                              
Coupled Cluster CCD         9.047     9.021       9.131             9.325 9.378
CCSD         9.035                              
CCSD(T)                       9.017 9.277   9.221 9.347     9.254  
CCSD(T)=FULL         8.933                           9.240  
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 cc-pV(D+d)Z cc-pV(T+d)Z aug-cc-pV(T+d)Z

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 10.384 9.473 10.335 9.428 10.517 10.373
density functional B3LYP 10.267 9.701 10.200 9.645 10.399 10.276
Moller Plesset perturbation MP2 8.910 9.053 8.895 9.032    
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.