Ab initio calculations and rate constant for the reaction H+H2

Different levels of ab initio theory are used to calculate geometries, vibrational frequencies and energies for stationary points on the H + H-2 -> H-2 + H reaction. Frequencies and geometries calculated for H-2 at the QCISD/cc-PVTZ and QCISD/aug-cc-PVTZ levels. of theory are in very good agreement with experiment. The ab initio frequencies and geometries for the transition state are similar to those for the Liu-Siegbahn-Truhlar-Horowitz and double many-body expansion surfaces. Based on these ab initio calculations, thermal rate constants are calculated for the reaction H + H2 -> H-2 + H using the conventional transition state theory, thermodynamic formulation of transition state theory and semi-classical transition state theory.