Phase Behavior of Materials under Extreme Conditions
Reinhard Boehler works on a broad range of problems in high pressure science and technology, particularly those related to major energy challenges.
At high pressure and high temperature, materials usually undergo phase transitions accompanied by significant changes in their physical and chemical properties. Melting is the transition that leads to the most dramatic changes in these properties since it results in a randomization in the atomic structure and a loss of material strength.
However, the structural aspects of this process are poorly understood. Melting played a key role in early differentiation of our planet and is key to understanding material properties in extreme stress/temperature environments. Experimental and theoretical work on melting properties at high pressure is often in very serious disagreement, but measurements of the melting curves have benefited greatly from the development of the laser-heated diamond-anvil cell.
This talk reviews the various methods of experimentally measuring melting temperatures at very high pressures and describes new developments combining pulsed laser heating with rapid synchrotron X-ray diffraction. These measurements provide first insights in the structural changes prior to and during the melting of materials.