Reinhard Boehler - Presentation & Short Bio

reinhard oehler

Biographical sketch

Reinhard Boehler studied Chemistry and Physics at the Universität Tübingen, Germany, and obtained his Bachelor degree in 1968, and his Master degree in Mineralogy in 1970 from the same Instituition.
In 1974 he obtained his PhD in Mineralogy from the Universität Tübingen, Germany. From then on, Reinhard Boehler worked as Assistant Research Geophysicist at the Institute of Geophysics and Planetary Physics (IGPP), University of California, Los Angeles, USA and was the Head of the High-Pressure Laboratory, IGPP, UCLA, USA untill 1986 and the Head of High-Pressure-Mineral Physics, Max-Planck-Institut f. Chemie, Mainz, Germany untill 2009.
He was president of AIRAPT from 2007 until 2011.
He is now a Senior Scientist at the Geophysical Laboratory in Carnegie Institution of Washington, and also at the Oak Ridge National Lab at the Spallation Neutron Source.

 

Abstract

“Unsolved phase diagrams of simple materials”
Reinhard Boehler,
Oak Ridge National Laboratory, Carnegie Institution, Washington

The remarkable increase in activity in high pressure research both experimental and theoretical has drastically changed not only the landscape but also the contradiction in phase diagrams of some important simple materials such as hydrogen, H2O ices, diamond and of course iron. As my contributions on hydrogen are minute, I will focus this talk on new, unpublished experiments on 1) H2(D2)O using novel neutron diffraction methods in the megabar range, 2) flash laser melting experiments on diamond, and 3) resistivity measurements on molten iron. For D2O, neutron diffraction makes it possible to see the onset of H-bond symmetrisation above about 60 GPa, signs of the ice X transition. This work, performed with novel, multi-carat diamond anvils at the Spallation Neutron Source in Oak Ridge, is in progress and at the time of the meeting, hopefully a clear picture can be presented. The phase behavior of diamond reveals a strongly negative melting curve, in stark contradiction with theory. It confirms the early ideas of a correlation in the phase diagrams of the group IV elements carbon, silicon and germanium. The consequence of this is metastability of diamond at very high pressures. For iron, changes in resistivity through both the solid-solid transition and at melting are very strong and unambiguous. They confirm a shallow melting curve and reveal very low conductivity of molten iron. Both findings put important constraints on the thermal history of the Earth’s core.