Lecture 1: Stacking of atoms

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Lecture 1 Stacking of atoms

• PHYS 430/603 material
• Laszlo Takacs
• UMBC Department of Physics

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Two consecutive layers of close packed hexagonal
layers of atoms

• ABC sequence of close packed hexagonal layers of
  atoms, leading to fcc structure.

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• Where is the cube in fcc?

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Two consecutive layers of close packed hexagonal
layers of atoms

• ABAB sequence of close packed hexagonal layers of
  atoms, leading to hcp structure.

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Seven circles fit together tightly and in only
one way on a plane, each neighbor touching each
other. This is not true for 13 spheres in 3-d
space the 12 spheres touching the central one do
not touch each other and can be arranged in
different ways. The lower image is an
icosahedron, fcc and hcp are other examples.
Space cannot be filled with tetrahedra alone
(top.)
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The bcc structure.Construction and the
closest-packed plane
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Interstitial sites in bcc structure
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Interstitial sites in fcc structure
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The structure of kaolinite, Al2O3 ? 2SiO2 ? 2H2O
Lower two layers Top three layers

• Layers from top
• O, OH
• Al
• O, OH
• Si
• O