The Potential Energy Profile of the HBr⁺ + HCl Bimolecular Collision

Recently, the HBr⁺ + HCl bimolecular reaction has been exploited by guided ion beam studies to probe the effect of rotational excitations and collision energies on the dynamics of the ion-molecule reactions. The current manuscript employs high-level ab initio calculations and reports the potential energy of pathways leading to various products, including HBr + HCl⁺, H₂Cl⁺ + Br, H₂Br⁺ + Cl, and H₂ + BrCl⁺. The study shows that the intermediates involved in this reaction are connected by low-lying transition states, thus frequent isomerizations and diverse products are expected. Further, this manuscript screens the performance of 192 different combinations of computationally efficient methods and basis sets in order to identify the optimal quantum chemical method for further dynamics simulations.