There is a growing appreciation that there may exist extensive interaction
between Earth's interior and the hydrosphere. The discovery of substantial
amounts of hydrogen in nominally anhydrous minerals, the possible
imbalance between water entering and exiting the mantle, and the discovery
of dense hydrous phases, have all contributed to increasing interest in
the state of water in Earth's interior. Earth's mantle is a potentially
vast storage site for water. Besides, incorporation of water in
crystalline and liquid silicates is known to affect rheological and
elastic properties in upper mantle minerals. Our goal is to address the
state of hydrogen in hydrous and nominally anhydrous silicates such as the
major phase of the lower mantle, MgSiO3-perovskite at relevant conditions.
What is the limit on the amount of H that can be stored in the mantle? How
much accompanies iron [III], aluminum, magnesium, silicon, and oygen
vacancies? Hydrogen in these sites is likely to be delocalized, transiting
between oxygen neighbors. (Truhlar, Wentzcovitch, and Baroni)
