STUDYING HYDROGEN AND WATER IN MINERALS AND IN SINGLE CRYSTALS

The role of hydrogen in minerals, their behavior under pressure that signifies conditions in the upper or lower mantle is of interest in many ways: It can be a source of water, it can change mineral and rock hardness and behavior, it can be a deciding factor that determines mineral properties and rock behavior. Understanding water binding and mobility in minerals is meaningful for environmental stability as well as applications.

Water and hydrogen in minerals are intensely studied and can be linked to tunneling and other effects that are of potential interest for industrial applications. Yet, hydrogen and hydrogen as part of structural water in a mineral structure is often elusive, treacherous to identify, quantify or position and lost among heavier surrounding elements in a structure solution, when powder or single crystal X-ray data are available.

Using neutron scattering is remarkably sensitive to hydrogen and water contained in a crystal structure arrangement. The scattering strength of hydrogen is comparable to surrounding and bound elements, carbon, oxygen, sulphur. Diffraction and spectroscopy are excellent tools to decipher the structural interplay and the

dynamic mechanisms that drive structural change.

External stimuli can drive structure changes under applied conditions, that allow hydrogen jumping. Studying the behavior of anisotropic displacement parameters often provides insight into kinetics or structure distortions critical for interesting chemical or physical properties.

Acknowledgement:

This research used resources at the High Flux Isotope Reactor and Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory (ORNL).