  Using a density-functional-theory-based approach, we explore the
symmetrization and proton dynamics in ice-VII, for which recent high-pressure
NMR experiments indicate significant proton dynamics in the pressure-range of
$20-95$ GPa. We directly sample the potential seen by the proton and find a
continuous transition from double- to single-well character over the pressure
range of 2 to 130 GPa accompanied by proton dynamics in agreement with the NMR
experiments.
