# Number of octahedral and tetrahedral voids present in a HCP structure

The given image depicts the tetrahedral and octahedral voids in HCP structure.

## For the tetrahedral part

I figured out that there would be 6 tetrahedral voids in total.

My visualisation: In the image, 3 inverted and 3 upright tetrahedron can be formed. Is this correct?

## For the octahedral part

It is hard to visualise the octahedrons for an atom. And so, I can't figure out the number of octahedral voids in HCP.

Also, I want to calculate how much part of the octahedron (see figure) is in each HCP structure.

Finally, the image shows only one octahedron. Can you help me in visualising the other octahedrons?

• Think of it in terms of hexagonal layers. Any two layers are positioned the same way as in fcc, hence there must be exactly as much voids of each type per atom. – Ivan Neretin Sep 28 '18 at 14:27