Is it possible to have a closed packed structure with hexagonal layers such that the atoms of second layer overlap the atoms of first layer , instead of overlapping the triangular voids ? ( like we do with square packed layers )

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Solution

Dear student,
No, It is not possible because if atoms in first layer and second layer overlap then there will be more vacant spaces in lattice due to more distance between first and second layer as compared to when they fit in voids, Hence packing fraction decreases. Therefore lattice can not be called closed packed structure.
Regards,

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