Theoretical Approach for the Structures, Energetics and Spectroscopic Properties of (H₂O₃)_n(n = 1-5) Clusters

Abstract

The geometrical parameters, vibrational frequencies, and binding energies for (H 2 O 3 ) n (n = 1-5) have been investigated using various quantum mechanical techniques. The possible structures of the clusters (n = 2-5) are fully optimized and the binding energies are predicted using energy differences at each optimized geometry. The harmonic vibrational frequencies are also determined and zero-point vibrational energies (ZPVEs) are considered for the better prediction of the binding energy. The best estimation of the binding energy for the dimer is 8.65 kcal/mol. For n = 2 and 3, linear structures with all trans forms of the HOOOH monomers are predicted to be the lowest conformations in energy, while the cyclic structures with all cis-HOOOH monomers are preferable structures for n = 4 and 5.

Theoretical investigation of the structures and spectroscopic properties of (H2O4)n (n = 1–4) clusters

“…The O‐H and O‐O bond distances of 1a agree with the previous theoretical results . The O‐H and O‐O bond lengths at the MP2/aug‐cc‐pVTZ level of theory were very similar to those for the trans‐HOOOH predicted at the same level of theory . However, the central O‐O bond length (1.405 Å) was significantly shorter than the outer O‐O distances (1.425‐1.435 Å).…”

“…The binding energy of 2b (after correcting for the BSSE) was −9.0 kcal/mol at the MP2/cc‐pVTZ level of theory. The best prediction at the CCSD(T)/cc‐pVTZ level of theory after the ZPVE and 50% BSSE corrections (−8.7 kcal/mol) was slightly larger (absolute value) than the binding energy of the H 2 O 3 dimer at the same level of theory (−8.65 kcal/mol) . The binding energy of the water dimer was experimentally estimated to be −3.6 ± 0.5 kcal/mol and theoretically predicted to be −3.2 ± 0.1 kcal/mol (including zero‐point and temperature effects) by Feyereisen et al; Keutsch and Saykally predicted a binding energy of −3.09 kcal/mol.…”

“…For the H 2 O 2 dimer, the H‐bond energy was predicted to be −7.28 kcal/mol at the MP4/6‐31++G(2d,2p) level and their best estimation was −5.36 kcal/mol after correcting for the ZPVE and BSSE . Here, the binding energies were predicted to be −3.0, −6.43, −8.65, and −8.7 kcal/mol for the H 2 O, H 2 O 2 , H 2 O 3 , and H 2 O 4 dimers, respectively, at the CCSD(T)/cc‐pVTZ level of theory (after the ZPVE and 50% BSSE corrections). This result implies that the thermodynamic stability increased for larger values of n in the H 2 O n dimers because of stronger intermolecular H‐bonding and because H 2 O 4 is a stronger proton donor (acid) but a weaker proton acceptor (base) than either H 2 O 2 or H 2 O 3 .…”

“…So far, many investigations of large water clusters have been published to characterize the H‐bonding effect in clusters . The IR spectrum and a theoretical study of the hydrogen peroxide (H 2 O 2 ) dimer were reported by Engdahl et al The structures and binding energies of (H 2 O 2 ) n ( n = 2–4) clusters were studied theoretically by Kulkarni et al The proton donor/acceptor character of H 2 O 2 in bulk liquid water and in the H 2 O 2 ‐H 2 O complex has been theoretically investigated by Martins‐Costa et al The H‐bonded (H 2 O 3 ) n clusters were investigated at different levels of theory by Kovačič et al and Seo et al However, an investigation of the (H 2 O 4 ) n complex has not been reported yet even though there are many studies of the H 2 O 4 monomer. The concentration of (H 2 O 4 ) n clusters under typical atmospheric conditions should be very low, and the competition with the formation of H 2 O 4 ‐water clusters reduces the formation of (H 2 O 4 ) n clusters.…”

Recent Advances in the Chemistry of Hydrogen Trioxide (HOOOH)

“…The binding energies per unit monomer in the trimers are greater than those in the dimers . Thus, there is a slight favorable cooperative effect in forming the long-chain structures.…”