Interstitial Defects: Introduction and Exploration

A interstitial defect is when an atom occupies a lattice site in between the sites of the atoms making up the normal crystal. You may have a intrinsic interstitial defect, also called a self-interstitital in which an atom from the host crystal is occupying its own interstitial sites. This would be an intrinsic defect because no foreign atoms are needed to form it. You can also have a interstitial impurity which would be extrinsic because there's a impurity, or foreign atom, in the host crystal.

NetLogo model 1.6.1 below is a molecular dynamics model like the one in the previous section, but now there is am interstitial atom. It is the small red atom in the middle. You can increase and decrease its size with the corresponding buttons. The way this is modeled is that instead of a single σ parameter in the Lennard-Jones potential (Eq. 1.2.1), each atom has its own σ and the interatomic potential between two atoms is calculated using the average of their σ parameters. The relative size of the atom compared to the host lattice is displayed in the "interstitial size" monitor on the left of the model.