These are likely due to the shallowness of the potential energy wells of the configurations of H3O + ; it may also be a consequence of the mobility of the proton. However, the true PES is a surface of zero-point corrected points by virtue of the Uncertainty Principle. Therefore, the energy optimized nature of the stationary points in figures 5E, 5F, 5[CE] ‡ and 5[EF] ‡ need to be approached with caution.