Materials Modelling Group: Defects in crystalline metals
InterfacesThe research is directed towards understanding the influence of interfaces on the physical properties of polycrystalline materials. Such understanding requires knowledge of the structure of interfaces and the processes that occur therein. Considerable progress has been reported in determining the structure of interfaces, but relatively few studies have revealed information about processes at atomic level, and these are our primary concern. We have investigated elementary processes in the hexagonal close packed (hcp) structure. This crystal system is of interest because plastic deformation is partly accommodated by twinning and so the mechanism of motion of twin boundaries and the interaction of such boundaries with other defects are of particular interest for the understanding of mechanical properties. Other interfaces considered are incommensurate in one direction and such research represent a preliminary step towards the study of defects in non-periodic boundaries. The research is extended to the atomic structure of tilt and twin boundaries in GaN semiconductors of wurtzite structure.
Defects produced in irradiated materials: point defects, clusters of point defects and dislocation loops
Radiation can produce dramatic changes in the microstructure and microchemistry of materials, which in turn can effect significant changes in properties. An understanding of the microstructural changes, which occur during irradiation, is critical for the development of predictive models and improvement of material behaviour during irradiation. Planar clusters of point defects and dislocation loops formed from vacancies and self-interstitial atoms are created in metals under irradiation. Consequences of the formation of glissile interstitial clusters are both, the creation of vacancy supersaturation that leads to swelling, and the decoration of dislocations that leads to the increase of the upper yield stress. Our research is focussed on the interaction of these clusters with the other defects of the microstructure.