Dr. John S. Tse [University of Saskatchewan, Saskatoon, Canada]

Title: High Pressure Studies on Greigite - the mineral of Life

Time: 10:00 - 11:00 AM, Thursday, May 19, 2016

Place: Conference Room C206, HPSTAR (Beijing)

Host: Dr. Mahmoud Abdel-Hafiez

Abstract:

In this presentation, I will report recent studies on the temperature and pressure dependent transformations of the magnetic and crystal structures of Greigite (Fe3S4), the sulphur analog of the well-known magnetite (Fe3O4). Using a myriad of synchrotron and laboratory characterization techniques complemented by theoretical electronic structure calculations, it was found that Fe3S4 behaves very differently from Fe3O4 in spite of the close similarity in their ambient crystal structures.  In particular, a spin transition to a metallic state was found to occur at 2.9 GPa, which is much lower than that observed in FeS.  Although a Verwey transition was predicted by theory, no metal-insulator transition was detected down to 4.2 K.  The advantages and disadvantages of in-situ high pressure Mossbauer spectra measured in the time and energy domain will be compared.

Biography of the Speaker:

John S. Tse started his research career in synchrotron radiation in 1975. After receiving his Ph.D. from the University of Western Ontario 1980, he moved to the Chemistry Division of the National  Research  Council  of Canada in  Ottawa as  an NSERC  Fellow. He was appointed scientific officer in 1981. In 1990, he moved to the newly created NRC Steacie Institute for Molecular Science. He progressed quickly through the ranks and achieved the highest level of principal research officer in 2000. He was the leader of the Theory and Computation Program from 1995 to 2004. Since 2004, he joined the University of Saskatchewan as a Tier One Canada Research Chair in the Department of Physics and Engineering Physics.

Dr. Tse has a very broad research interest at the converging frontiers of chemistry and physics. During  his  undergraduate  years,  he  worked  as  a  researcher  in  the  x-ray  crystallography laboratory helping to solve crystal structures. His first scientific paper in 1975 was on the elucidation of the structure of Dacron. In his early career, he made several ground-breaking contributions to natural gas hydrates, an abundant source of fossil energy. A notable example is the theory he developed to explain the anomalous glass-like thermal conduction behaviour of crystalline gas hydrates. This theory was later adopted as a new paradigm on the rational design of efficient thermoelectric materials. His interest in high-pressure science started in early 1990 when he explained the phenomenon of pressure amorphization of crystalline solids. For this work, he was awarded the 1995 Chemical Society of Canada Noranda (later the Keith Laidler) award for a physical chemist under the age of 45. He advanced concepts on the design of superalloys, Li ion batteries, thermoelectric and hydrogen storage materials. He is an internationally recognized expert in ice physics. Since moving to the university, he has focused on the superconductivity behaviour of dense hydrogen alloys and magnetic single-molecule radical solids under compression. He co-discovered the first molecular insulator to metal transition in 2012.  Dr. Tse has published over 500 articles and 18 reviews and book chapters on diverse subjects.  Many of the papers appeared in the most prestigious scientific journals such as Nature, Science, Phys. Rev. Letts., Proc. Nat. Acad. Sci.,… etc. He has presented over 200 lectures at international conferences  and  workshops.  His h-index is 51 with close to 10,000 citations. He has served  on  many  national  and international committees.

He was elected to a Fellow of the Royal Society of Canada in 2008 and received the Distinguished Researcher Award of the University of Saskatchewan in 2010 and earned a D.Sc. in 2012.