# Tetrahedral Sites

| In a tetrahedral site the interstitial is in the center of a tetrahedra forms by four lattice atoms. Three atoms, touching each other, are in plane; the fourth atom sits in the symmetrical position on top.
|  | Again, the tetrahedral site has a defined geometry and offers space for an interstitial atom.
|  | The configuration on top is the tetrahedral position in the fcc lattice. The black circles denote lattice points, the red circle marks one of the 8 the tetrahedral position.
|  |  | The picture on the bottom shows the tetrahedral configuration for the bcc lattice. We have (6 · 4)/2 = 12 positions per unit cell.

With frame

1.3.3 The larger View and Complications

Interstitials

Octahedral sites

2.1.2 Frenkel Defects

Ionic Crystals

© H. Föll (Defects - Script)