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Accurate ab initio intermolecular potential energy surface for the quintet state of the O2(3Σ(-)(g))-O2((3)Σ(-)(g)) dimer

AuthorsBartolomei, Massimiliano ; Carmona-Novillo, Estela ; Hernández, Marta I. ; Campos-Martínez, José ; Hernández-Lamoneda, Ramón
KeywordsVan der Waals
Log-derivative method
O2-O2 dimer
O2 Molecules
Heisenberg exchange
[PACS] Coupled-cluster theory
[PACS] Intermolecular and atom-molecule potentials and forces
[PACS] General molecular conformation and symmetry; stereochemistry
[PACS] Vibrational analysis (molecular spectra)
[PACS] Potential energy surfaces (atoms and molecules)
[PACS] Ab initio calculations (atoms and molecules)
Issue Date3-Jun-2008
PublisherAmerican Institute of Physics
CitationJournal of Chemical Physics 128(21): 214304 (2008)
AbstractA new potential energy surface (PES) for the quintet state of rigid O2(3Σ(-)(g))+O2((3)Σ(-)(g)) has been obtained using restricted coupled-cluster theory with singles, doubles, and perturbative triple excitations [RCCSD(T)]. A large number of relative orientations of the monomers (65) and intermolecular distances (17) have been considered. A spherical harmonic expansion of the interaction potential has been built from the ab initio data. It involves 29 terms, as a consequence of the large anisotropy of the interaction. The spherically averaged term agrees quite well with the one obtained from analysis of total integral cross sections. The absolute minimum of the PES corresponds to the crossed (D-2d) structure (X shape) with an intermolecular distance of 6.224 bohrs and a well depth of 16.27 meV. Interestingly, the PES presents another (local) minimum close in energy (15.66 meV) at 6.50 bohrs and within a planar skewed geometry (S shape). We find that the origin of this second structure is due to the orientational dependence of the spin-exchange interactions which break the spin degeneracy and leads to three distinct intermolecular PESs with singlet, triplet, and quintet multiplicities. The lowest vibrational bound states of the O2–O2 dimer have been obtained and it is found that they reflect the above mentioned topological features of the PES: The first allowed bound state for the 16O isotope has an X structure but the next state is just 0.12 meV higher in energy and exhibits an S shape.
Description10 pages, 5 figures, 3 tables.-- PACS nrs.: 31.15.bw; 34.20.Gj; 33.15.Bh; 33.20.Tp; 31.50.-x; 31.15.A-.
Publisher version (URL)http://dx.doi.org/10.1063/1.2929852
Appears in Collections:(CFMAC-IFF) Artículos
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