An analogy is constructed between the known composition of elemental sulfur (principally S8rings) and the unknown oxygen rings. Due to the weakness of Ondash;O single bonds, as in hydrogen peroxide, it is hypothesized that oxygen rings are potential high energy density materials. A particularly attractive candidate is the O4molecule, for which ring strain is expected to provide further destabilization relative to two separated O2molecules. To pursue these qualitative suggestions,abinitiomolecular quantum mechanics has been employed. Both selfhyphen;consistent field (SCF) and configuration interaction including single and double excitations (CISD) methods have been employed in conjunction with double zeta plus polarization basis sets. At the highest level of theory the nonplanar (D2dpoint group, Ondash;Ondash;Ondash;O torsional angle 25deg;) equilibrium structure is predicted to lie 2.9 kcal below the planarD4hstructure, which is a transition state. The infrared spectrum is predicted at the DZ+P CISD level, as well as lower levels of theory. The O4minimum is predicted to lie sim;100 kcal/mol above the asymptotic limit of two O2molecules.
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