General theory of the Kanzaki force field: static and dynamic models of dislocations and other extended defects

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• Dr Benat Gurrutxaga-Lerma, CUED
• Friday 15 February 2019, 14:30-15:00
• Oatley Seminar Room, Department of Engineering.

If you have a question about this talk, please contact Hilde Hambro.

The Kanzaki forces are the standard way of representing point defects in the elastic continuum. They are the forces that would have to be applied on a perfect, defect-free crystalline lattice to generate the topology of the point defect. By computing these forces in atomistic lattices, one obtains a true multiscale representation of the defect.

In this talk, I generalise the concept of Kanzaki forces to all other crystalline defects. I will discuss how the resulting Kanzaki force fields are to be computed for any general defect, including dislocations, grain and twin boundaries, or cracks.

I will then focus on crystallographic dislocations. I will show that the Kanzaki force field of a dislocation consists of two separate components: a Volterra contribution associated with the disregistry that characterises the dislocation, and a core contribution associated with the specific topology of the dislocation core.

I will then show how to use each of these components to model the dislocation core in the elastic continuum. Unlike other regularisation procedures like the Peierls-Nabarro model, the resulting models are topologically true to the dislocation core, and energetically accurate up to the harmonic approximation.

Finally, I will discuss how the Kanzaki force field can be employed to study dislocation mobility using lattice dynamics, and I will highlight several lattice instabilities that arise when screw and edge dislocations are driven at high speeds.

This talk is part of the Engineering - Mechanics and Materials Seminar Series series.

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