Ab initio global potential-energy surface for H5+→H3++ H2 -: art. no. 224307

An accurate global potential-energy surface (PES) is reported for H-5(+) based on more than 100 000 CCSD(T)/aug-cc-pVTZ ab initio energies. This PES has full permutational symmetry with respect to interchange of H atoms and dissociates to H-3(+) and H-2. Ten known stationary points of H-5(+) are characterized and compared to previous ab initio calculations. Quantum diffusion Monte Carlo calculations are performed on the PES to obtain the zero-point energy of H-5(+) and the anharmonic dissociation energy (D-0) of H-5(+)-> H-3(+)+H-2. The rigorous zero-point state of H4D+ is also calculated and discussed within the context of a strictly classical approach to obtain the branching ratio of the reaction H4D+-> H-3(+)+HD and H2D++H-2. Such an approach is taken using the PES and critiqued based on the properties of the quantum zero-point state. Finally, a simple procedure for adding the long range-interaction energy is described.