Table 5. Energies Relative to Isomer A (kcal/mol) and Zundel/Eigen Character of Low-Energy Isomers of H+(H2O)22a.
| isomer | RIMP2b | DFTB2 | DFTB3-diag+gaus | DFTB3/3OB | DFTB3/3OBw | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| A | 0.0 | (E) | (E) | 0.0 | (Z) | (E-Z) | 0.0 | (E) | (E) | 0.0 | (E) | (E) | 0.0 | (E) | (E) |
| B | 9.5 | (E) | (E) | 8.8 | (Z) | (E-Z) | 6.2 | (E) | (E) | 7.0 | (E) | (E) | 9.1 | (E) | (E) |
| C | 2.9 | (E) | (E) | 0.9 | (Z) | (E-Z) | 2.1 | (E) | (E) | 2.5 | (E-Z) | (E) | 2.5 | (E-Z) | (E) |
| D | 7.4 | (E) | (E) | 1.9 | (Z) | (E-Z) | 0.0 | (E) | (E) | 1.8 | (E) | (E) | 5.2 | (E) | (E) |
| E | 6.5 | (E) | (E) | 4.1 | (Z) | (Z) | 1.2 | (E) | (E) | 2.2 | (E) | (E) | 5.5 | (E-Z) | (E) |
| F | 5.3 | (E) | (E) | 2.6 | (Z) | (Z) | 3.3 | (E) | (E) | 1.5 | (E) | (E) | 1.8 | (E) | (E) |
| G | 9.8 | (E-Z) | (E) | 6.9 | (Z) | (Z) | 5.3 | (E) | (E) | 7.0 | (E) | (E) | 10.5 | (E) | (E) |
| H | 2.7 | (E) | (E) | 1.8 | (E-Z) | (E) | –1.2 | (E) | (E) | 0.5 | (E) | (E) | 3.8 | (E) | (E) |
| I | 2.4 | (E) | (E) | 1.7 | (Z) | (E) | –1.4 | (E) | (E) | 0.4 | (E) | (E) | 4.5 | (E) | (E) |
| J | 0.5 | (E) | (E) | 1.6 | (E-Z) | (E) | 1.0 | (E) | (E) | 1.1 | (E) | (E) | 0.9 | (E) | (E) |
| K | 12.0 | (E) | (E) | 8.0 | (Z) | (E-Z) | 6.6 | (E) | (E) | 7.8 | (E) | (E) | 9.8 | (E) | (E) |
| L | 3.4 | (E) | (E) | 4.5 | (Z) | (E-Z) | 3.3 | (E) | (E) | 3.3 | (E) | (E) | 4.0 | (E) | (E) |
| M | 6.8 | (E) | (E) | 3.9 | (Z) | (Z) | 4.5 | (E) | (E) | 5.2 | (E-Z) | (E) | 6.3 | (E-Z) | (E) |
a
In the column for each method, the three subcolumns indicate the energy relative to isomer A, the Z/E/E-Z classification according to the criterion based on ROO,132 and the Z/E/E-Z classification according to the criterion based on δ.100
b
The RIMP2 relative energies are from ref (133). The RIMP2 results therein were obtained by single-point calculations with the aug-cc-pVTZ basis set at B3LYP/6-31+G(d) optimized geometries. The Z/E/E-Z classification is based on the B3LYP/6-31+G(d) geometries.