讲座题目：Oxidation States underPressure: Challenging Two Long-Held Paradigms

讲座嘉宾：John S.Tse 加拿大皇家科学院院士 加拿大萨斯喀彻温大学教授

讲座时间：2026年9月15日（星期二）14：30

讲座地点：中心校区唐敖庆楼B521报告厅

嘉宾简介：

Professor John S. Tse isa materials scientist whose career spans chemistry, physics, computationalmaterials science, synchrotron science, mineral physics, and high-pressureresearch. He integrates first-principles electronic-structure calculations withhigh-pressure experiments using neutron and synchrotron X-ray spectroscopy tounderstand material behaviour.

Professor Tse earned hisB.Sc. in Chemistry from The Chinese University of Hong Kong and his Ph.D. inChemistry from the University of Western Ontario. He began his research careerat the National Research Council of Canada, where he became a PrincipalResearch Officer and led the Theory and Computational Project. In 2004, hejoined the University of Saskatchewan as a Tier I Canada Research Chair in SynchrotronScience, and he is now a University Distinguished Professor.

Professor Tse’sscientific work covers a broad range of cross-disciplinary subjects. He hasmade contributions across several major areas of condensed-matter and materialsphysics. In clathrate hydrates, he established the molecular mechanismsgoverning gas trapping and hydrate nucleation, providing fundamental insightinto energy storage and planetary ices. In ice physics, his work on amorphousand high-pressure ice revealed the structural origin of water polyamorphism andthe transformations between crystalline and amorphous phases, advancing ourunderstanding of water under extreme conditions. In thermoelectric materials,he developed first-principles theories linking electronic structure, latticedynamics, and anharmonic phonon transport to the design of high-efficiencythermoelectrics with low thermal conductivity. In high-pressuresuperconductivity, he conducted quantum-mechanical studies of hydrogen-richcompounds. He contributed to the first discovery of hydride superconductors andsingle-molecule magnets.

His scientificaccomplishments have been recognized through many national and internationalhonours, including the Noranda Award of the Chemical Institute of Canada,Steacie Institute for Molecular Sciences Outstanding Achievement Awards,recognition as a STINT Fellow, Sweden, James M. Flaherty Visiting Professor,Ireland-Canada Foundation, election as a Fellow of the Royal Society of Canada,and appointment as a Distinguished Professor and Centennial Enhancement Chairof the University of Saskatchewan. More recently, he received the InauguralDistinguished Alumni Award from the Faculty of Science of The ChineseUniversity of Hong Kong.

讲座摘要：

Oxidationstate is one of the most powerful qualitative concepts in chemistry. Itprovides a useful framework for describing electron transfer, bonding, andchemical reactivity, although it is not equivalent to the actual charge orionicity of an atom. Under high pressure, however, extension of this familiarinterpretation becomes less straightforward. Compression substantiallyincreases orbital overlap and introduces strong interactions betweenneighbouring atoms, leading to electron redistribution, charge delocalization,and changes in bonding that may not occur under ambient condition.

In thispresentation, two long-held concepts are critically examined: the assignment ofoxidation states in iron-bearing minerals and the interpretation ofpressure-induced valence changes in the lanthanides. Experimental observationsare combined with first-principles electronic-structure calculations todistinguish formal oxidation states from measurable changes in charge densityand orbital occupation. The results show that the assignment of oxidation statecan become ambiguous under strong compression and may not reliably representthe actual valence-electron configuration or chemical behaviour of an atom.

主办单位：科学技术协会

承办单位：物理学院

          物质模拟方法与软件教育部重点实验室