报告摘要：The chemical composition of the Earth’s core and the behavior of light elements under extreme conditions remain fundamental questions in Earth science. Hydrogen is one of the most likely candidates for a light element in the core, but its effect on the volume and density of iron under core conditions needs to be better understood. Using high pressure neutron diffraction experiments at the PLANET beamline, J.PARC, we have investigated hydrogen bearing iron alloys and found that the hydrogen induced volume expansion of Fe is significantly enhanced by the addition of Ni and Si. This result suggests that the amount of hydrogen required to explain the density deficit of the core may be lower if Si is present in the core. The underlying mechanism may involve local repulsive interactions between Si and H.

I will also discuss our recent studies of nitrogen storage in the deep mantle. Ferropericlase can form oxynitrides under reducing conditions, suggesting that the “missing nitrogen” may be stored in the lower mantle. I will further discuss the potential role of bridgmanite as a nitrogen-bearing phase.

报告人简介：Hiroyuki Kagi is a Professor at the Geochemical Research Center, Graduate School of Science, the University of Tokyo. He received his Ph.D. in Chemistry from the University of Tokyo and has conducted research in geochemistry, mineral physics, and high pressure science for more than three decades. His research focuses on understanding the chemical and physical processes occurring in the deep Earth, with particular emphasis on the behavior of hydrogen and other light elements in minerals and metals under extreme pressure and temperature conditions. He has continued the application of neutron diffraction, synchrotron X ray diffraction, and spectroscopic techniques to high pressure Earth and planetary materials. He played a leading role in the development of PLANET beamline, the high-pressure neutron diffractometer at J.PARC, which has become an important facility for high-pressure materials research. His recent research includes hydrogen in iron and iron alloys, high pressure phases of ice, and the behavior of volatile and light elements in deep Earth materials. He received the Geochemical Society of Japan Award and the Japan Society of High Pressure Science and Technology Award.

联系人：邓正、靳常青

联系电话：82649163