An ab initio molecular orbital study of some binary complexes of water.
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Date
1996
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Abstract
Ab initio molecular orbital theory has been successful in predicting the stabilities
of many weak complexes; typical of these are the complexes formed between
water and various small molecules. To account for the correlation effect, Moller-Plesset
perturbation theory truncated at the second order level was employed. In
order to account for the hydrogen bonding, the 6-3lG** basis set was used.
The geometry optimisations of the complexes were carried out using the
Gaussian-92 suite of programs installed on a Hewlett-Packard 720 computer
operating under UNIX.
The interaction energies of the complexes were subjected to further analysis by
applying the Morokuma decomposition scheme. The electrostatic interaction
component accounts for over 40% of the total stabilisation energy in all the
typical hydrogen bonded complexes. Gas phase enthalpies were computed and
compared with the experimental values of similar systems. For the systems
studied here, the prediction is that all complexes are stable at 25° C.
A second program, Vibra, was used for carrying out a normal coordinate
analysis. A third computer program for the graphical representation of molecular
and crystallographic models, Schakal-92, was employed to illustrate the
predicted equilibrium geometries and the fundamental vibrational modes.
The predicted geometries, interaction energies, charge redistributions, vibrational
wave numbers, infrared intensities and force constants are listed and compared
with those in the literature, where applicable. Correlations between the various
predicted properties show some interesting chemistry.
Description
Thesis (Ph.D.)-University of Natal, Durban, 1996.
Keywords
Quantum chemistry., Molecular orbitals., Molecular structure--Data processing., Water chemistry., Gaussian basis sets (Quantum mechanics), Theses--Chemistry., Hydrogen bonding.