Question

Select the correct statement (S) related to hexagonal close packing of identical spheres in three dimensions:

• A. In one unit cell there are 12 octahedral voids and all are completely inside the unit cell.
• B. In one unit cell there are six octahedral voids and all are completely inside the unit cell.
• C. In one unit cell there are six octahedral void and out of which three are completely inside the unit cell and other three are from contribution of octahedral void which are partially inside the unit cell
• D. Co-ordination number of every sphere is 12 in hcp lattice.

Answer 1

Answer: (B), (D)

The correct options are
B In one unit cell there are six octahedral voids and all are completely inside the unit cell.
D Co-ordination number of every sphere is 12 in hcp lattice.

HCP $=ABABAB$........................... pattern report

For calculation voids between two layers $A$ and $B$.

Octahedral voids $=3=$ represented by (*).

So total octahedral voids $=6=$ All are completely inside.