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| In this paper the hydrogen binding energies in water clusters (H2O)n (n=3-20) are estimated with a polarizable two-dipole model. In this polarizable two-dipole model we regard the two O-H bonds of a water molecule as two dipoles. The magnitude of the O-H bond dipole moment can be varied by the presence of a second water molecule. An analytic potential energy function eq. (9), which explicitly contains the permanent dipole-dipole interactions, the polarization interactions, the van der Waals interactions and the covalent interactions, is therefore established. The hydrogen bonding energies in water clusters (H2O)n (n=3-20) are then evaluated by using eq. (9) and compared with those obtained from MP2/aug-cc-pVTZ calculations including BSSE corrections and with those obtained from AMBER99, CHARMM19 and OPLSAA/L force fields. The results show that the hydrogen bonding energies produced by eq. (9) are as accurate as those produced by MP2/aug-cc-pVTZ calculations with BSSE corrections, much better than those produced by the three force fields. Calculation results also show that the permanent dipole-dipole interaction is the most important part in hydrogen bonding interaction. |
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| Keywords:hydrogen bonding energies; polarization; water clusters; dipole-dipole interaction |
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