On Thursday, September 13th, 2018 the department of Mechanical and Materials Engineering had the pleasure of hosting another instalment of the Distinguished Speaker Series. This talk featured Dr. Chung Woo (previously of Atomic Energy of Canada Limited, and Emeritus Professor of Solid-State Electronics, The Hong Kong Polytechnic University) and his thoughts on “Integrating atomistic processes in irradiation damage models: issues and effects”.

An overview of the talk can be found below:

In an engineering description of irradiation damage accumulation, micromechanics in the atomistic scales of time and space has to be transposed to the macroscopic or thermodynamic scales. Rate-theory model began with a continuum description of microstructure evolution as the result of the balance of the generation, migration and annihilation at sinks of crystal defects. Equal production of vacancies and SIAs was assumed. Atomistic mechanics is integrated via reaction rate constants based on an elastic continuum theory assuming isotropic diffusion-controlled kinetics.

The continuum model neglects the discreteness, structure and dynamics of the crystal lattice. Reaction constants for non-cubic defects depend on the orientation of the sink relative to that of the diffusivity. Lattice and spin waves affect activation dynamics and the applicability of the Arrhenius law. The thermodynamics, mobilities and diffusivities of migrating defects, dislocation dynamics, reaction kinetics and nucleation probabilities are all affected.

Equal production of vacancies and SIAs neglects the effect of cascades and sub-cascades. The unequal occurrence and unequal thermal stability of the in-cascade primary defect clusters means a strongly temperature-dependent production bias which has far-reaching consequences in irradiation-damage modeling.

All in all, it was a fantastic turn out! Thank you to Dr. Chung Woo for taking the time to visit Queen’s University and share your thoughts.

Be on the lookout for future talks in the Distinguished Speaker Series such as Dr. Jerry Cuttler on the “Health effects of low doses or low dose-rates of ionizing radiation” on Tuesday, October 9th, 2018 in Botterell Hall room B143.