MATTER LogoIntroduction to Crystallography

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Crystal Structures > Packing of Atoms

Description of Flash Animation.

This animation shows a close-packed layer where each atom is in contact with six others on the same layer and a square packed layer where each atom is in contact with four others on the same layer.

This resource requires Flash Player 9 or above available to download from http://www.adobe.com/go/getflash

In order to try to understand how different structures can arise, we can represent atoms as hard spheres.

If we pack equal spheres as tightly as possible on a level surface, this hexagonal arrangement is called a close packed layer. If the layer extends to infinity, each atom is in contact with six others in the same layer.

Another way we can pack atoms is in a square array. This packing is not as dense as the gaps (interstices) between the atoms are larger. Each atom is in contact with four other atoms in the same layer.

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