Ekhard Salje

Ferroelastic phase transitions

Ferroelastic phase transitions in oxides and other materials are characterised by twin walls which can be moved under external stress. The mobility of the walls and the internal structure are of major importance for the understanding and the application of ferroelastics. Research starts from the following observations:

1.

Domain walls have a thickness of several tens of interatomic distances. Although their orientations is roughly determined by the compatibility relation, their actual trajectories are determined by the elastic response due to the formation of intermediate structures, such as needle domains.

2.

Internal structures of domain walls are often electronic in nature (e.g. superconducting twin walls in an insulating matrix) and need to be considered in theories which go beyond the continuums approximation.

3.

Domain patterns are significantly changed by surface relaxations (e.g. the funnel effect). Their analysis is crucial for the assessment of chemical diffusion through surfaces in ferroelastics. The potential for cooperation with other groups was stressed.