Quasielastic neutron scattering for analyzing transport dynamics of chemically-bound hydrogen in minerals

We demonstrate that quasielastic neutron scattering is effective for analyzing transport dynamics of chemically-bound hydrogen cations within crystal structures of minerals. In this report, our recent results of its application for hydrogen in brucite Mg（OH）₂ are described. We observed two types of hydrogen transport dynamics, which included（i）jump within a single two-dimensional layer of hydrogen lattice, and（ii）jump from a layer into the next-nearest layer. The former observed at ≥ 230 K is ascribed to surface diffusion within basal planes of brucite grains, while the latter observed at 430 K is ascribed to proton conduction through the interior of the grains. These transport dynamics observed in the prototypical two-dimensional structure of brucite will have implication for understanding of hydrogen transport mechanisms occurring within various types of mineral structures