1. Water Hexamers
Stability Ordering

2. What I will talk about reasons to research differences in structures
differences in ways to calculate
inconclusive conclusions

3. Water is phenomenal Ice Structure Hydrogen Bonding
Climate/Ocean Currents

4. Why Water Hexamers?
Smaller water clusters (n=3-5) have an almost two dimentional structure
Larger clusters (n=7-12) maintain a more 3-D shape
The six oxygens in the water hexamer represent the transition from a more flat to a more 3-D shape

5. Two Structures
ring prism

6. more hexamers
cage bag

7. ~more hexamers~
boat book

8. one more hexamer
chair

9. Question
How does the stability of different shapes of water hexamers change, with and without the inclusion of zero point energy?

10. Stabilities without ZPE (kcal/mol)
PM3 HF
PBE
PBE1W
BLYP
B3LYP
boat
bag
prism
0.52
0.13
0.24
0.16
cage
0.25
0.11
chair
0.69
0.27
0.39
0.37
0.2
ring
0.87 1
0.43
0.59
0.47
1.1
book
0.45
1.8
1.4
1.5
1.7
0.88
2.2
1.6
1.3
0.96

11. Zero Point Energy
ZPE – the vibrations of a molecule at 0 Kelvin

12. The stabilities with ZPE(kcal/mol)
PM3 HF
PBE
PBE1W
BLYP
B3LYP
prism
0.00
cage
1.36
0.55
0.74
0.17
0.65
0.52
bag
2.19
0.59
1.04
0.22
1.42
0.80
boat
2.36
2.25
2.58
ring
1.47
2.68
2.26
book
2.99
2.28
2.82
chair
1.51
3.97
3.19
3.02
3.90
2.95
1.72
5.54
4.54
3.18
3.00
1.87
5.55
4.58

13. Comparison
The results were a little more uniform when ZPE was included

16. Method details PM3 HF/aug-cc-pVTZ (for O)and cc-pVTZ (for H)
MP2/(same as HF)*
DFT methods:
PBE/aug-cc-pVTZ
PBE1W/6-311+G(2d,2p)
BLYP/6-31+G(d,p)
B3LYP/6-31+G(d,2p)
*(still to come)

17. References: Favorite articles:
- Kozmutza, C.; Kryachko, E.S.; Tfirst, E. THEOCHEM, 2000, 501, 435.
- Ludwig, R. Ange. Chem. Intl. 2001, 40, 1809.
- Yoshioki, S. J. Mol. Graphics and Modelling 2003, 21, 487.
Favorite people:
- Erin Dahlke
- Professor Truhlar
Thanks MSI!