STRUCTURE AND THERMOCHEMISTRY OF CLO2 RADICALS

The structure Of ClO2 has been calculated for the X2A'' ground state u sing unrestricted Hartree-Fock (UHF), unrestricted second-order Moller -Plesset perturbation (UMP2), configuration interaction using single a nd 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 angstr om. The single-configuration based QCI in the singles and doubles spac e with perturbation inclusion of triple substitutions, denoted QCISD(T ), yield a ClO bond length of 2.205 angstrom. The QCI results are cons istent with results of Jensen who showed that the CIO bond length is 2 .181 angstrom using annihilated self-consistent methods (AUMP2). The t hermochemistry Of ClO2 radical has been calculated using MP2 and QCI m ethods using an isodesmic scheme. Our scheme predicts the heat of form ation for ClO2 at 0 K to be 24.6 +/- 2 kcal mol-1.