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Calculated Ionization Energy for H2O (Water)

20 09 09 14 00
Experimental Ionization Energy is 12.621 ± 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
composite G2 12.550
G3 12.515
G3B3 12.527
G3MP2 12.513
G4 12.513
CBS-Q 12.580

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) 6-311+G(3df,2p) TZVP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(T+d)Z daug-cc-pVTZ
hartree fock HF 7.975 10.200 10.200 10.723 10.683 10.679 10.881 10.715 10.725 10.681 10.892 10.820 10.612 10.785 10.834 10.892 10.861 10.861 10.785 10.857
density functional BLYP 9.200 11.334 11.334 11.986 12.023 12.044 12.488 12.158 12.191 12.035 12.548 12.429 11.951 12.341   12.525 12.536   12.340  
B1B95 9.354 11.434 11.434 12.023 12.069 11.791 12.405 12.152 12.186 12.095 12.484 12.377 12.016 12.298 12.381 12.439 12.430 12.435 12.299  
B3LYP 9.381 11.524 11.524 12.147 12.177 12.191 12.565 12.289 12.317 12.190 12.621 12.515 12.107 12.446 12.542 12.598 12.603 12.608 12.446  
B3LYPultrafine   11.524     12.177 12.191 12.565 12.289   12.190 12.621 12.515 12.107 12.446   12.598 12.603      
B3PW91 9.391 11.565 11.565 12.148 12.172 12.184 12.503 12.269 12.297 12.185 12.555 12.451 12.113 12.399   12.534 12.527   12.399  
mPW1PW91 9.336 11.518 11.518 12.089 12.107 12.116 12.433 12.193 12.219 12.117 12.478 12.373 12.047 12.319   12.465 12.450   12.303  
M06-2X 9.442 11.643 11.642 12.167 12.207 12.217 12.509 12.317 12.347 12.249   12.502 12.162 12.485   12.557 12.600      
PBEPBE 9.258 11.460 11.460 12.079 12.113 12.131 12.532 12.224 12.260 12.127 12.588 12.473 12.054 12.395 12.498 12.572 12.575 12.580 12.395  
PBEPBEultrafine   11.460     12.113 12.131 12.532 12.224   12.127 12.588 12.473 12.054 12.395   12.572 12.575      
PBE1PBE 9.260 11.466 11.466 12.047 12.066 12.066 12.398 12.149 12.179 12.078 12.445 12.345 12.007 12.288   12.431 12.424      
HSEh1PBE 9.251 11.458 11.458 12.037 12.058 12.070 12.393 12.144 12.173 12.068 12.440 12.343 11.995 12.284   12.423 12.418      
TPSSh 9.252 11.409 11.409 11.979 11.982 11.987 12.315 12.084 12.095 11.981 12.360 12.262 11.905 12.197 12.282 12.338 12.335 12.345    
wB97X-D 9.406 11.583 11.583 12.175 12.211 12.222 12.531 12.285 12.307 12.219 12.562 12.430 12.265 12.385 12.458 12.550 12.505 12.509    
B97D3 9.405 11.536 11.537 12.125 12.152 12.167 12.532 12.249 12.279 12.167 12.579 12.459 12.097 12.387 12.484 12.569 12.548 12.557    
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) 6-311+G(3df,2p) TZVP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(T+d)Z daug-cc-pVTZ
Moller Plesset perturbation MP2 8.231 10.979 10.979 11.725 11.961 12.055 12.395 11.989 12.151 12.251 12.678 12.335 11.949 12.506 12.697 12.545 12.705 12.778 12.506  
MP2=FULL 8.231 10.981 10.981 11.726 11.965 12.061 12.401 11.996 12.160 12.259 12.689 12.341 11.954 12.520 12.712 12.551 12.722 12.792 12.520  
MP3         11.762   12.177       12.387 12.073 11.756 12.247            
MP3=FULL   10.875 10.875 11.563 11.765 11.866 12.152 11.779 11.935 12.057 12.398 12.077 11.760 12.259   12.285 12.422      
MP4   10.929     11.788       12.015   12.542 12.190 11.797 12.369   12.400 12.572      
MP4=FULL   10.929     11.793       12.022   12.553   11.802 12.382   12.404 12.589      
B2PLYP 8.942 11.278 11.278 11.937 12.019 12.057 12.416 12.099 12.167 12.117 12.541 12.362 11.966 12.365   12.489 12.538      
B2PLYP=FULL 8.943 11.278 11.278 11.937 12.020 12.058 12.418 12.101 12.170 12.119 12.545 12.364 11.967 12.369   12.491 12.543      
B2PLYP=FULLultrafine 8.943 11.278 11.278 11.937   12.058 12.418 12.101 12.170 12.119 12.545 12.364       12.491        
Configuration interaction CID   10.839 10.839 11.516 11.669     11.694     12.247   11.655 12.111            
CISD   10.835 10.835 11.508 11.662     11.696     12.254   11.651 12.112            
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) 6-311+G(3df,2p) TZVP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(T+d)Z daug-cc-pVTZ
Quadratic configuration interaction QCISD   10.885 10.885 11.578 11.752 11.846 12.157 11.792 11.933 12.033 12.400 12.090 11.746 12.246   12.293 12.417   12.245  
QCISD(T)         11.764     11.821     12.482 12.143 11.770 12.318   12.350 12.507   12.318  
QCISD(T)=FULL         11.767   12.193       12.493   11.775 12.331 12.514 12.354 12.524 12.587    
QCISD(TQ)         11.771   12.187       12.469   11.774 12.308 12.486 12.343 12.491 12.556    
QCISD(TQ)=FULL         11.774   12.192       12.480   11.779 12.322 12.501 12.347 12.508 12.570    
Coupled Cluster CCD   10.888 10.888 11.586 11.759 11.853 12.146 11.789 11.931 12.037 12.384 12.079 11.750 12.241   12.274 12.401   12.241  
CCSD         11.752 11.846 12.150 11.789 11.930 12.032 12.392 12.083 11.745 12.241 12.404 12.283 12.408 12.468    
CCSD=FULL         11.755         12.039 12.403 12.088 11.750 12.254 12.418 12.287 12.424 12.481    
CCSD(T)         11.764 11.868 12.186 11.820 11.974 12.078 12.478 12.139 11.770 12.316 12.497 12.346 12.503 12.570 12.316  
CCSD(T)=FULL         11.767           12.489 12.144 11.774 12.329 12.512 12.350 12.520 12.583    
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) 6-311+G(3df,2p) TZVP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(T+d)Z daug-cc-pVTZ

Ionization Energies in eV
Methods with effective core potentials (select basis sets)
CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD cc-pVTZ-PP aug-cc-pVTZ-PP Def2TZVPP
hartree fock HF 10.770 10.723 10.796 10.742 10.777 10.778     10.831
density functional BLYP                 12.446
B1B95                 12.402
B3LYP 12.186 12.188 12.222 12.233 12.272 12.267     12.534
B3LYPultrafine                 12.534
B3PW91                 12.469
mPW1PW91                 12.391
M06-2X                 12.525
PBEPBE                 12.489
PBEPBEultrafine                 12.490
PBE1PBE                 12.363
HSEh1PBE                 12.361
TPSSh                 12.274
wB97X-D 12.135 12.153 12.180 12.199 12.235 12.231     12.458
B97D3                 12.477
Moller Plesset perturbation MP2 11.849 12.077 11.937 12.142 11.882 11.886     12.590
MP2=FULL                 12.598
MP3                 12.316
MP3=FULL                 12.323
MP4=FULL                 12.457
B2PLYP                 12.452
B2PLYP=FULL                 12.455
B2PLYP=FULLultrafine                 12.455
Configuration interaction CID                 12.176
CISD                 12.180
Quadratic configuration interaction QCISD                 12.319
QCISD(T)                 12.396
QCISD(T)=FULL                 12.403
QCISD(TQ)                 12.385
QCISD(TQ)=FULL                 12.392
Coupled Cluster CCD                 12.310
CCSD                 12.313
CCSD=FULL                 12.320
CCSD(T)                 12.393
CCSD(T)=FULL                 12.400
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.