Possible O8+–O12+ Structures Obtained by Use of Classical Electrostatic Theory

The interaction energy in the series O₂–O₆⁺ through 3O₂–O₆⁺ is approximated as the sum of the van der Waals interactions between the neutral species and the following electrostatic interactions: monopole–quadrupole, quadrupole–quadrupole, and (monopole+quadrupole)–induced dipole+induced dipole–induced dipole. Two planar O₆⁺ structures and charge distributions obtained by the CDO–IBM method were used in the O₈⁺ computations. The computed dissociation energy $D_e({\mathrm{O}}_2–{\mathrm{O}}_6^{+})$ is certainly too large for the O₆⁺ structure with the larger charge on the central O₂. The $D_e$ values computed for the O₆⁺ structure of smaller charge are as follows: $D_e({\mathrm{O}}_2{\mathrm{–O}}_6^{+}{\text{)\hspace{0.17em}=\hspace{0.17em}3.42, D}}_e({\mathrm{O}}_2–{\mathrm{O}}_8^{+}\text{)\hspace{0.17em}=\hspace{0.17em}3.26,}\mathrm{and}{D}_e({\mathrm{O}}_2–{\mathrm{O}}_{10}^{+}\text{)\hspace{0.17em}=\hspace{0.17em}3.12}\mathrm{kcal}/\mathrm{mole}$ . Although these values are larger than the experimental $\mathrm{\Delta H°}$ data, they are in reasonable agreement considering the uncertainties in the van der Waals potential and the quadrupole moments and the lack of data concerning the higher moments and polarizabilities, e.g., the quadrupole polarizability. The O₈⁺–O₁₂⁺ have been studied at $\text{T\hspace{0.17em}<\hspace{0.17em}100°K}$ . The barriers to internal rotation by the attached O₂ molecules are computed to be 1.2 kcal, much larger than $\mathrm{RT}$ for $\text{T\hspace{0.17em}<\hspace{0.17em}100°K}$ .