AN ACCURATE QUANTUM MONTE-CARLO CALCULATION OF THE BARRIER HEIGHT FOR THE REACTION H+H2-]H2+H

An improved quantum Monte Carlo method has been used to calculate the classical barrier height for the hydrogen exchange reaction H + H-2 --> H-2 + H with accuracies greater than previously attained. The method is exact in that, except for the easily estimated Monte Carlo statistical or sampling error, it requires no mathematical approximations or physical approximations beyond those of the Schrodinger equation. The minimum in the barrier, occurring for the collinear nuclear configuration with the protons separated by 1.757 bohrs, was found to be 9.61 +/- 0.01 kilocalories per mole above H + H-2.