MIE Special Seminar on Spin-lattice dynamics investigation of magnetic effects on vacancy formation and migration in bcc iron by Dr. C. H. Woo from the City University of Hong Kong, China
Abstract: Ferritic/martensitic (F/M) steels and their variants are important candidate materials for Generation IV fission reactors (core and pressure vessel applications) as well as fusion reactors (first walls and blankets). They are ferromagnetic below the Curie temperature, so that thermodynamics of atomic processes must include contributions from the atomic spins. As a result of the coupling of the dynamics of the atoms and those of the spins, the strong temperature dependence of the magnetic properties can be transmitted to the lattice. Examples of this kind of coupling are commonly seen in the thermal expansion, elastic anomaly, phonons frequencies, etc., in ferromagnetic metals. In this talk, we report on our investigation on how vibrational thermodynamics of vacancy formation and migration in bcc iron is affected by ferromagnetism. A combination of spin-lattice dynamics and modified thermodynamic integration (TI) method is used. Energetic and entropic contributions to vacancy formation and migration of bcc iron are obtained as a function of temperature. Effects due to the relaxation of spin correlations during the vacancy processes near the FM/PM phase boundary are discussed.
Brief Bio: C. H. Woo is Chair Professor of Nuclear Engineering of Hong Kong CityU, Emeritus Professor of Hong Kong PolyU and is an academician of the Hong Kong Academy of Engineering Sciences. His Ph.D. was from University of Waterloo in Theoretical Solid State Physics, and D.Sc. from HKU in Materials Science and Engineering. He was Senior staff scientist with Atomic Energy of Canada (AECL) before joining Hong Kong PolyU in 1996, where he held Chair Professorships in Mechanical Engineering and Solid-State Electronics before retiring and leaving for CityU in 2012. He did research on basic materials science in areas of irradiation-damage accumulation, deformation mechanisms, and Ferroelectric Tunnel Junctions.
Friday, October 3, 2014 at 4:00pm to 5:00pm
Dodge Hall, 450