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Placing third layer over the second layer
Placing second layer over the first layer
o Consider a two dimensional hexagonal close packed layer of type‘ A’ and place a similar layer above it in such a way that the spheres of the second layer lies in the depressions of the first layer.
o Let the second layer be of type‘ B’ due to its different alignment.
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All the triangular voids of the first layer are not covered by the spheres of the second layer which gives rise to a different arrangement.
The area where a sphere of the second layer is above the void of the first layer( or vice versa) a tetrahedral void is formed.