| Empirical | Name | Expt. |
PM6-ORG |
PM6-D3H4X |
PM6-D3H4 |
PM6 |
PM7 |
| H4O2 | Water dimer Structure 1 (Non-planar open Cs) | -5.00 |
0.30 |
-0.22 |
-0.22 |
1.04 |
0.30 |
| H4O2 | Water dimer Structure 2 (Open Ci) | 0.52 |
0.36 |
0.22 |
0.22 |
0.31 |
0.36 |
| H4O2 | Water dimer Structure 3 (Planar Open Cs) | 0.57 |
0.24 |
-0.04 |
-0.04 |
0.09 |
0.24 |
| H4O2 | Water dimer Structure 4 (Cyclic Ci) | 0.70 |
0.13 |
0.53 |
0.53 |
-0.41 |
0.13 |
| H4O2 | Water dimer Structure 5 (Cyclic C2) | 0.95 |
0.45 |
0.76 |
0.76 |
-0.18 |
0.45 |
| H4O2 | Water dimer Structure 6 (Cyclic C2h) | 0.99 |
0.52 |
0.51 |
0.51 |
-0.40 |
0.52 |
| H4O2 | Water dimer Structure 7 (Triply Hydrogen Bonded | 1.81 |
-1.88 |
0.34 |
0.34 |
-0.88 |
-1.88 |
| H4O2 | Water dimer Structure 8 (Non-planar Bifurcated | 3.57 |
-1.31 |
0.25 |
0.25 |
-0.90 |
-1.31 |
| H4O2 | Water dimer Structure 9 (Non-planar Bifurcated | 1.79 |
-1.75 |
0.11 |
0.11 |
-1.06 |
-1.75 |
| H4O2 | Water dimer Structure 10 (Planar Bifurcated C2v | 2.71 |
-1.82 |
-0.18 |
-0.18 |
-1.29 |
-1.82 |
|
Source of the reference data: Tschumper, G. S., et al. (2002). "Anchoring the water dimer potential energy surface with explicitly correlated computations and focal point analyses." The Journal of chemical physics 116(2): 690-701. (The geometry of "Water dimer Structure 1 (Non-planar open Cs)" can be seen here.) The lowest-energy conformation of the water dimer is Structure 1. This is 5.0 Kcal/mol more stable than the two separate water molecules. The energies of the other conformers, Structures 2-10, are all relative to Structure 1. |