Hydrogen Bonds under Extreme Conditions: Nuclear Quantum Effects and Hydrogen Bond Symmetrisation Probed with 1H-NMR in Diamond Anvil Cells

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Hydrogen bonds are ubiquitous in nature and often influence structural and electronic properties of hydrogen bonded materials to a degree which is still not fully understood. This class of materials include numerous minerals and materials within the Earth and planetary bodies; thus, investigations of pressure effects on H-bonds are not only important for basic physics and chemistry, but also matter greatly for geo-and planetary sciences on a macroscopic "global scale". Therewith, in this proposal, rarely observedpressure induced nuclear quantum effects occurring even at ambient temperatures will be investigated on the example of high pressure ices and hydrous minerals, by means of a newly developed high pressure NMR technique in diamond anvil cells (DACs). These methods provide a singular vantage point of these exotic quantum phenomena, which cannot be detected with comparable spectroscopic methods used within the high pressure research community. To this extent, the elusive transition from high pressure ice VII to X will be investigated, which has been reported to occur between 70 and 150 GPa. Within this pressure range, the symmetric double-well potential of the hydrogen bond allows for proton tunneling across the energy barrier. Elucidation of these combined effects might answer some of the most controversial questions in modern high pressure sciences, such as the hydrogen transport into regions of Earth's interior.Hydrogen bond symmetrisation is expected to be a general feature in high-pressure behaviour of different compounds (particularly delta-AlOOH, MgSi2O6H2, FeOOH), and by studying them at megabar pressures by means of NMR (and complimentary techniques like single-crystal X-ray diffraction and vibrational spectroscopies), we expect to reveal regularities in pressure induced proton nuclear quantum effects in H-bonds.