Absence of proton tunneling during the hydrogen-bond symmetrization in

Abstract

is of significant crystallochemical interest due to a subtle structural transition near 10 GPa from a to a structure, the nature and origin of hydrogen disorder, the symmetrization of the O- hydrogen bond and their interplay. We perform a series of density functional theory-based simulations in combination with high-pressure nuclear magnetic resonance (NMR) experiments on up to 40 GPa with the goal to better characterize the hydrogen potential and therefore the nature of hydrogen disorder. Simulations predict a phase transition in agreement with our NMR experiments at and hydrogen bond symmetrization at . Calculated hydrogen potentials do not show any double-well character and there is no evidence for proton tunneling in our NMR data.