Dr. Alexander Goncharov [Geophysical Laboratory, CIW, USA]

Title: Novel high-pressure materials with unusual bonding patterns and stoichiometries

Time: 10:00 - 11:00 AM, Friday, December 18, 2015

Place: Conference Room 201, HPSTAR (Shanghai)

Abstract:

Diamond anvil cells (DAC) made it possible to explore extreme energy-density regimes that are of relevance for planetary interiors and extreme physics and chemistry. How different is chemistry rules at high pressure have been a topic of many recent studies that found a number of empirically derived principles that govern the modification of chemical bonds in conditions of increased density. DAC experiments in the Mbar pressure range have shown a variety of novel phenomena in elementary materials and compounds. First principles structure search methods have been very instrumental in new material predictions that often possess unusual chemical bonding and stoichiometry. In this study, we explore a synergy between theory and experiment to investigate emerging chemistry laws at extreme conditions. We will give examples of recent studies of K-Cl, C-N, N-H, Na-He, Mg-O, Na-H systems that revealed the formation of novel compounds that become thermodynamically stable at high pressures and can be synthesized in the pressure-temperature range of their thermodynamic stability. These materials revealed a wide range of metastability holding a promise for synthesis of materials with unique physical and chemical properties for a variety of applications. This investigation has a direct relevance for planetary interiors as the compounds synthesized in this study can exist as alternative planetary ices or mantle/core minerals. I thank A. R. Oganov, S. Lobanov, and E. Stavrou for contributing greatly to this work.

Biography of the Speaker:

Dr. Alexander F. Goncharov, member in Hefei Institutes of Physical Science Chinese Academy of Sciences (CASHIPS), Institute of Solid State Physics (ISSP), was presented with The 2015 People's Republic of China Friendship Award on September 29th, 2015. Vice Premier Ma Kai issued the award to Alexander Goncharov and other foreign experts. The Friendship Award is the People's Republic of China's highest award to commend foreign experts who have made outstanding contributions to China's economic and social progress.

He was awarded combined BSc and MSc degrees in physics from Moscow Institute of Physics and Technology, Russia in 1979. After that, he moved to Institute for Spectroscopy, Russian Academy of Science and obtained a PhD in Physics in 1983. He is working in Institute of Solid State Physics of Chinese Academy of Sciences. He is also a senior staff scientist of Geophysical Laboratory of the Carnegie Institution for Science since 2003. At the Carnegie, he pioneered a suit of spectroscopy measurements in diamond anvil cells at very high pressures in excess of 200 GPa (2 million atmospheres) at high temperatures above 6000 K. He had research positions in Lawrence Livermore National Laboratory of USA, Max-Planck-Institute für Festkörperforschung of Germany and Institute of Crystallography, Russian Academy of Sciences of Russia. He is a recognized expert in a multitude of experimental techniques in diamond anvil cells, including optical and synchrotron spectroscopy, and thermal properties at high-temperature and high-pressure extreme conditions. His research interests cover condensed-matter physics, simple molecular solids, the chemistry and physics of the Earth’s mantle and core, and high-pressure materials science. He has published nearly 200 papers in journals like Nature, Science, and Physical Review Letters with over 5000 citations.