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Meier, Thomas ; Petitgirard, Sylvain ; Khandarkhaeva, Saiana ; Dubrovinsky, Leonid:
Observation of nuclear quantum effects and hydrogen bond symmetrisation in high pressure ice.
In: Nature Communications.
Bd. 9
(2018)
.
- 2766.
ISSN 2041-1723
DOI: https://doi.org/10.1038/s41467-018-05164-x
Abstract
Hydrogen bond symmetrisations in H-bonded systems triggered by pressure-induced nuclear quantum effects (NQEs) is a long-known concept but experimental evidence in high-pressure ices has remained elusive with conventional methods. Theoretical works predicted quantum-mechanical tunneling of protons within water ices to occur at pressures above 30 GPa, and the H-bond symmetrisation transition to occur above 60 GPa. Here we used 1H-NMR on high-pressure ice up to 97 GPa, and demonstrate that NQEs govern the behavior of the hydrogen bonded protons in ice VII already at significantly lower pressures than previously expected. A pronounced tunneling mode was found to be present up to the highest pressures of 97 GPa, well into the stability field of ice X, where NQEs are not anticipated in a fully symmetrised H-bond network. We found two distinct transitions in the NMR shift data at about 20 GPa and 75 GPa attributed to the step-wise symmetrisation of the H-bond.