Microsolvation-induced quantum localization in protonated methane.

Nuclear quantum effects are responsible for vivid large-amplitude motion in protonated methane CH(5)(+), which enables so-called "hydrogen scrambling" that leads to the dynamical equivalence of all five protons even at low temperatures. But what is the impact of external perturbations on hydrogen scrambling of CH(5)(+) in this quantum fluxional ground state? We report ab initio path integral simulations of CH(5)(+)(H(2))(n), n = 1, 2, 3 that demonstrate cessation of hydrogen scrambling at low temperatures (20 K), but only slowdown at moderate temperatures (110 K). Importantly, different and unexpected mechanisms that are responsible for freezing the scrambling dynamics are revealed and traced back to distinct microsolvation patterns.