Grain Boundary dynamics from atomistic calculations
J. Pezold, L. Lymperakis, and J. Neugebauer
The mobility of the Grain Boundaries (GBs) is a key mechanism which determines the microstructural evolution during growth: It controls the processes of recrystallization, grain growth, phase transformation, and precipitation. Therefore it determines the grain size and subsequently the yield strength in the post grown material.
The aim of the present project is:
- To provide quantitative information about the GB mobility.
- To identify those atomic scale mechanisms which control the GB mobility, such as uncorrelated atomic shuffle motion and formation and kinetics of interface kinks.
A major obstacle in the molecular dynamics description of the GB mobility is the introduction of a suitable driving force. While various approaches are available in the literature, not all of them are able to sustain the motion for any kind of GB and/or to describe the dependence of the GB mobility on any of the five relevant misorientation and boundary inclination degrees of freedom. Therefore in the first stage of the project the different approaches are tested and the validity and suitability of the corresponding driving forces are considered.
- Animation of the evolution of a bi-crystal system containing two equivalent Σ7 Grain Boundaries at T=800 K. The misorientation dependent driving force is used.
The γ surface constitutes an alternative approach to investigate the GB dynamics. The advantage of this approach is that it directly combines the atomist scale calculations with continuum mechanics. In a joined project with the ICAMS 'Micromechanical and Macroscopic Modeling' department , the γ surfaces of various special Al GB have been calculated using EAM potentials.
Ab-initio based growth simulations of III-Nitride nanostructures
Third order elastic constants of III-Nitride alloys
