Ab Initio Calculations and Many Body Analysis of the Water Tetramer
Cyclic and chainlike structures of hydrogen bonds have been observed experimentally in crystal structures of molecules of biological interest which contain hydroxy1-groups and cocrystal1ize with water (Betzel et al. 1984; Zabel et al. 1986; Vernon et al. 1982). Beyond the additive energy of these arrangements there is a stabilization caused by cooperative effects (Clementi et al. 1980). The additional energy gained in these associates is explained by the polarizabi1ity of the 0-H groups which are able to function as donors and acceptors in homo-, anti- or hetero-oriented extended hydrogen bonding patterns. Cyclic structures are preferred over chainlike ones because they contain the maximum number of bonds (Saenger 1979; Del Bene et al. 1970). The analysis and the definition of a measure for the amount of hydrogen bond cooperativity is the subject of this investigation.
KeywordsHydrate Pyrimidine Purine Barbiturate
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