return to home page

XVII.C.1.

Calculated Ionization Energy for H2O (Water)

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
semi-empirical PM3  
composite 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) TZVP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(T+d)Z
hartree fock HF 7.974 10.199 10.199 10.723 10.683 10.679 10.881 10.715 10.725 10.681 10.820 10.612 10.785 10.834 10.892 10.861 10.861 10.785
density functional SVWN   12.197     12.954   13.385                      
BLYP 9.200 11.335 11.335 11.986 12.023 12.043 12.488 12.158 12.191 12.035   11.951 12.340         12.340
B1B95 9.351 11.461 11.461 12.062 12.069 12.119 12.447 12.192 12.224 12.128   12.046 12.299 12.381 12.440 12.431 12.435 12.299
B3LYP 9.381 11.524 11.524 12.147 12.177 12.192 12.565 12.289 12.317 12.190 12.515 12.107 12.446 12.542 12.598 12.603 12.608 12.446
B3LYPultrafine         12.177                          
B3PW91 9.391 11.565 11.565 12.148 12.172 12.184 12.502 12.269 12.297 12.185   12.113 12.399         12.399
mPW1PW91 9.337 11.499 11.518 12.089 12.090 12.099 12.417 12.176 12.219 12.117   12.030 12.303         12.303
M06-2X         12.206                          
PBEPBE 9.258 11.460 11.460 12.079 12.113 12.131 12.532 12.224 12.260 12.127   12.054 12.395 12.498     12.580 12.395
PBE1PBE         12.067                          
HSEh1PBE         12.571                          
TPSSh             12.315                      
Moller Plesset perturbation MP2 8.231 10.979 10.979 11.725 11.961 12.055 12.395 11.988 12.151 12.251 12.335 11.949 12.506 12.697 12.546 12.706 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   11.954 12.520 12.712     12.792 12.520
MP3         11.762                          
MP3=FULL         11.765   12.152                      
MP4   10.929     11.788       12.015       12.887          
B2PLYP                         12.365          
Configuration interaction CID   10.839 10.839 11.515 11.669     11.694                    
CISD     10.835 11.508 11.662     11.696                    
Quadratic configuration interaction QCISD   10.885 10.885 11.578 11.752 11.846 12.157 11.792 11.933 12.033   11.746 12.245         12.245
QCISD(T)         11.764             11.770 12.318   12.350 12.508   12.318
Coupled Cluster CCD   10.888 10.889 11.586 11.759 11.852 12.146 11.788 11.931 12.038   11.750 12.241   12.274 12.401   12.241
CCSD         11.750                          
CCSD(T)         11.764             11.770 12.316 12.497 12.346 12.503 12.569 12.316
CCSD(T)=FULL         11.767                 12.512     12.583  

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 10.770 10.723 10.795 10.742 10.777 10.778
density functional B3LYP 12.186 12.189 12.222 12.233 12.272 12.267
Moller Plesset perturbation MP2 11.849 12.077 11.937 12.142 11.882 11.886
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.