Polymorf - Knowhwere- Diamond structure

Diamond structure elements

C (diamond), Si, Ge, a-Sn (gray)

Crystal lattice

The diamond crystal lattice structure can be modeled as an expanded FCC lattice

where one-half of the tetrahedral cluster of close packed atoms have another equal

radius atom of the same species located in the center of the cluster. But the volume

of the central sphere is larger than the size of the interstitial void space normally

present in the center of a tetrahedral cluster of closest packed atoms. This causes

the atoms located at the corners of the cluster to expand apart to accommodate the

central atom so that they no longer touch each other, only the central atom. Each

atom of the diamond packing has a coordination number of four compared to the

twelve coordinated atoms of a normal FCC packing.

In the following model of the diamond lattice one-half of the tetrahedra are

identified with an opaque color to indicate they contain a central atom (unoccupied

tetrahedral voids are blue).

Polyhedral framework

The polyhedral framework of elements exhibiting the diamond structure can be

modeled as a array of vertex linked tetrahedra with the understanding that each

tetrahedron contains a central equi-radius atom.

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linking surfaces
		Figure 54 - Polyhedral framework
		model of the diamond structure

4 vertices		click image to enlarge
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Page 36 - Structure matters - Diamond structure elements