Comparison of multireference configuration interaction potential energy surfaces for H + O2 → HO2: the effect of internal contraction

A comparison is presented of uncontracted multireference singles and doubles configuration interaction (MRCI) and internally contracted MRCI potential energy surfaces for the reaction \({\text{H}}\left( {^{2} {\text{S}}} \right) + {\text{O}}_{2} \left( {^{3} \sum\nolimits_{g}^{ - } {} } \right) \to {\text{HO}}_{2} \left( {^{2} {\text{A}}^{{\prime \prime }} } \right)\). It is found that internal contraction leads to significant differences in the reaction kinetics relative to the uncontracted calculations.