Benchmark calculations of the complete configuration-interaction limit of Born-Oppenheimer diagonal corrections to the saddle points of isotopomers of the H+H2 reaction -: art. no. 224313

We present a detailed ab initio study of the effect that the Born-Oppenheimer diagonal correction (BODC) has on the saddle-point properties of the H-3 system and its isotopomers. Benchmark values are presented that are estimated to be within 0.1 cm(-1) of the complete configuration-interaction limit. We consider the basis set and correlation treatment requirements for accurate BODC calculations, and both are observed to be more favorable than for the Born-Oppenheimer energies. The BODC raises the H+H-2 barrier height by 0.1532 kcal/mol and slightly narrows the barrier-with the imaginary frequency increasing by similar to 2%.