InorganicVII

Chapters / Chapter 1 · Solid state / Topic 5 of 14

Close packing in 1D and 2D

Chapter 1 · Solid state and crystal structures

1D row: CN = 2Square packing AAA: CN = 4Hexagonal ABAB: CN = 6
One dimension, then two: square packing is less efficient than hexagonal packing.

Close packing in one dimension

Spheres are placed in a row, each touching two neighbours. Coordination number = 2.

Close packing in two dimensions

Square packing (AAA type). Rows are placed one above the other so that spheres sit directly on top of each other. It is less efficient. Coordination number = 4.

Hexagonal packing (ABAB type). The second row sits in the depressions (holes) of the first row. This is the closest packing in two dimensions. Each sphere touches six neighbours. Coordination number = 6.