6. Electronic structure

The electronic structure of grain boundaries is a very important factor in the electrical, electronic and optical properties of materials, particularly semiconductors, oxides and other ceramics. The introduction of electronic levels into the band gap by defects, and in particular grain boundaries, has been a lively area of research for many years. The "intrinsic" properties of joints are the subject of controversy, as they may contain dislocations and/or steps, which can be the site of dopant segregation or impurity trapping.

The calculation of the electronic structure can be approached with different approximations (§ 5.1