Metallic Crystals - The Structures of Pure Metals
Animation of the Closest-Packed Structures
Animation of the closest-packed structures (front and top views)
The following two animations are designed to demonstrate the formation of the hexagonal and cubic closest-packed structures:
All of the closest-packed structures have in common the high coordination number of 12 (6 neighbors in the same layer + 3 above + 3 below) and a high percentage of occupied space (74 %). The unoccupied space consists of two types of holes:
- Octahedral holes are surrounded by six spheres arranged octahedrally. N spheres are accompanied by N octahedral holes. These are larger than tetrahedral holes.
- Tetrahedral holes are surrounded by four spheres in a tetrahedron. A structure containing N spheres contains 2N tetrahedral holes.