Table 3.
LEWIS predictions for small neutral water clusters and comparison with QM results. (Refs. 75 and 89) Here n denotes the number of monomers and nhb the number of hydrogen bonds. The formation enthalpy is given by ΔE = (Ecluster – n EH2O), and the energy per hydrogen bond is given by ΔEhb = (ΔE / nhb). For O-O distances (rOO), ranges are given. QM distances are taken from the structures provided by one of the authors (S.X.) of the QM references. The twisted prism hexamer of LEWIS is compared with the straight prism hexamer predicted by QM. The latter has nine hydrogen bonds.
| −ΔE | −ΔEhb | rOO | rOO, QM | −ΔEQM | |||
|---|---|---|---|---|---|---|---|
| Cluster | n | nhb | (kJ/mol) | (kJ/mol) | (Å) | (Å) | (kJ/mol) |
| (H2O)2 | 2 | 1 | 25.27 | 25.27 | 2.85 | 2.91 | 20.85 |
| (H2O)3 | 3 | 3 | 72.71 | 24.24 | 2.74–2.76 | 2.79 | 66.28 |
| (H2O)4 | 4 | 4 | 137.2 | 34.29 | 2.69–2.70 | 2.73 | 115.68 |
| (H2O)5 | 5 | 5 | 188.7 | 37.73 | 2.63–2.67 | 2.71–2.72 | 151.90 |
| (H2O)6,cycle | 6 | 6 | 235.4 | 39.23 | 2.63–2.64 | 2.71 | 187.61 |
| (H2O)6,prism | 6 | 7 | 234.6 | 33.52 | 2.62–2.84 | 2.65–2.95 | 192.01 |
| (H2O)8, D2d | 8 | 12 | 361.3 | 30.11 | 2.70–2.87 | 2.67–2.84 | 305.39 |
| (H2O)8,S4 | 8 | 12 | 361.3 | 30.10 | 2.69–2.91 | 2.66–2.84 | 304.72 |