ABSTRACT
In the previous chapter we gave considerable detail about how an atomistic model of a crystal can be developed and used to analyse the bulk properties. We spoke only about perfect crystals, with periodically repeated unit cells. A large fraction of the subject of the materials science of solids is based upon imperfect crystals that contain chemical impurities or other point defects. The next chapter is devoted to a description of selected theoretical calculations for point defects in insulators. Section 11.2 presents some results for classical diffusion, and describes two fundamental defect mechanisms: vacancy diffusion and interstitial diffusion. The reader is referred to that discussion at this time. The movement of ions, atoms and molecules through a crystal is responsible for a host of properties. We mention only a very few examples at this time. A more wide-ranging discussion can be found in works devoted to solid state diffusion, such as that by Borg and Dienes (1988).
