What are tetrahedral and octahedral sites in a crystal structure?

A tetrahedral site lies in the center of a 4-atom cluster within the crystal. In the picture at left, the tetrahedral site is the space between spheres, marked by the glow. The top sphere is lifted slightly to reveal the site. When atoms of the same size are packed together as closely as possible, there are two tetrahedral sites per atom.

An octahedral site is a space at the center of a cluster of six atoms that form an octahedron. The octahedral space is larger than the tetrahedral site. When atoms of the same size are packed as closely together as possible, there is one octahedral site for each atom.

Author: Fred Senese senese@antoine.frostburg.edu

General Chemistry Online! What are tetrahedral and octahedral sites in a crystal structure?