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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:

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Fig.1
Animation of the cubic and hexagonal closest-packed structures (side view)
Fig.2
Animation of the cubic and hexagonal closest-packed structures (top view)

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.
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