title: Note: "Exact" quantum Monte Carlo calculations of the barrier for the H + H2 reaction at the sub-microhartree level.
abstract: We report the third in a series of 'exact' quantum Monte Carlo calculations for the potential energy of the saddle point of the barrier for the reaction H + H2 → H2 + H. The barrier heights determined are 9.61 ± 0.01 in 1992/94, 9.608 ± 0.001 in 2003, and 9.6089 ± 0.0001 in 2016 (this work), all in kcal/mole and successively a factor of ten more accurate. The new value is below the lowest value from explicitly correlated Gaussian calculations and within the estimated limits of extrapolated multireference configuration calculations.
authors.affiliation: Department of Chemistry and Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: James B
authors.initials: JB
authors.lastname: Anderson