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Question
In case of hcp structure, how are spheres in first, second and third layers arranged?
Solution
- Hexagonal close-packed structure is obtained by stacking two dimensional hexagonal close-packed layers.
- So, the spheres in the first layer are arranged to form two dimensional hexagonal close packing.
- The spheres of the second layer are placed in the depressions of the first layer. If the first layer is labelled as ‘A’ layer, the second layer is labelled as ‘B’ layer because the two layers are aligned differently.
- The spheres of the third layer are aligned with the spheres of the first layer. The resulting pattern of the layers will be ‘ABAB....’. This arrangement results in a hexagonal close-packed (hcp) structure.
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