Efficient, Direct Calculation of Reaction Rate Coefficients Based on a Partially Rearranged Rovibrational Hamiltonian: A Full-Dimensional Case Study of the H2 + D → HD + H Reaction.

It is shown that an efficient, "direct", and fully quantum mechanical calculation of thermal reaction rate coefficients requires a new, partially rearranged form of the numerically constructed exact kinetic energy part of the rovibrational Hamiltonian expressed in internal coordinates. Using this Hamiltonian and an accurate, full-dimensional potential energy surface characterizing the H2 + H exchange reaction, developed by Mielke, S. L.; et al.J. Chem. Phys.2002, 116, 4142-4161., reaction rate coefficients in the temperature range of 75-800 K have been computed for the H2 + D → HD + H reaction. The paper puts particular emphasis on the exact treatment of overall molecular rotation and on nuclear spin symmetry.