STRUCTURE AND THERMOCHEMISTRY OF CLO2 RADICALS

The structure Of ClO2 has been calculated for the X2A'' ground state using unrestricted Hartree-Fock (UHF), unrestricted second-order Moller-Plesset perturbation (UMP2), configuration interaction using single and double excitation (CISD), and quadratic configuration interaction (QCI) ab initio molecular orbital methods. Calculations using UMP2 and CISD wave functions predict a CIO bond length of 1.728 +/- 0.01 angstrom. The single-configuration based QCI in the singles and doubles space with perturbation inclusion of triple substitutions, denoted QCISD(T), yield a ClO bond length of 2.205 angstrom. The QCI results are consistent with results of Jensen who showed that the CIO bond length is 2.181 angstrom using annihilated self-consistent methods (AUMP2). The thermochemistry Of ClO2 radical has been calculated using MP2 and QCI methods using an isodesmic scheme. Our scheme predicts the heat of formation for ClO2 at 0 K to be 24.6 +/- 2 kcal mol-1.