Accurate calculations of the rate constants and kinetic isotope effects for tritium-substituted analogues of the H + H₂ reaction

Rate constants are calculated for isotopic analogues of H + H₂ → H₂ + H. The calculations are distinguished by (i) use of the most accurate potential energy surface available for any reaction, (ii) use of variational-transition-state theory, (iii) consistent inclusion of anharmonicity, and (iv) calculation of tunneling contributions by a three-dimensional quantum-mechanical analogue of the collinear semiclassical Marcus-Coltrin procedure. On the basis of previous comparisons of ts kind of calculation to experimental data for five other isotopic analogues and to other theoretical calculations, we estimate the absolute accuracy of the calculations as approximately ±50%, at least for 300-1000 K.