O. Mo et al., STRUCTURE, VIBRATIONAL FREQUENCIES AND THERMODYNAMIC PROPERTIES OF HYDROGEN PEROXIDE-WATER DIMERS - AN AB-INITIO MOLECULAR-ORBITAL STUDY, Chemical physics letters, 219(1-2), 1994, pp. 45-52
High levels of ab initio molecular orbital theory have been used to st
udy the structures, binding energies, vibrational frequencies and equi
librium constants of hydrogen peroxide-water dimers. The geometries of
the different possible conformers were optimized at the HF/6-311 + +G
(2d, 2p) level of theory. Five different stationary points have been c
haracterized at this level, but only two are minima. The geometries an
d vibrational frequencies of these two minima were refined at the MP2/
6-311 + G(d, p) level. The stretching vibrations of the proton donors
show a sizable red-shift. The global minimum corresponds to a five-mem
bered ring, where both monomers behave simultaneously as proton donors
and proton acceptors. In the second minimum. which lies about 2.2 kca
l/mol higher, the hydrogen peroxide monomer behaves as a proton accept
or, while water behaves as a proton donor. The binding energies of the
se two species were obtained at the QCISD(T)/6-311 + G(2d, 2p) level u
sing the MP2 optimized geometries, and the corresponding equilibrium d
imerization constants evaluated. A topological analysis of the electro
nic charge densities of the dimers is presented.