Hidden Oceans: Proton disorder in high-pressure minerals

Scheme of the Earth’s mantle showing the path of water incorporation in the mantle. The hydroxyl defect structures realized in ringwoodite are given on the left side.

Hidden Oceans: The earth’s mantle can act as a potential reservoir for a vast amount of water exceeding the amount present in oceans. Hereby the water is stored in the form of hydroxyl sites charge balanced by cation vacancies in dense magnesium silicate structures. The nature of these defect sites is of great importance since it may have significant influence on mantle properties like viscosity and thermal conductivity. In collaboration with the BGI, we benefit from unique high-pressure devices and sophisticated synthesis strategies, which are essential for a successful sample preparation. In combination with high-resolution 1D and 2D solid-state NMR and quantum-mechanical calculations we gain insights in the structures and distributions of these hydroxyl defects.