how many second neighbours are in hcp and fcc - Chemistry - The Solid State

Question

how many second neighbours are in hcp and fcc?

Priya G N · Accepted Answer

For FCC and HCP systems, the coordination number is 12 ie the first
nearest neighbours are 12 and the second nearest neighbours are
6

In HCP there are three atoms in the center plane that are at the
second neighbour distance from the central basal plane atom By
symmetry, there are three more atoms in the center plane beneath
the basal plane, making a total of six second nearest neighbors The
second nearest neighbours for HCP is 6
In FCC, we
can see that there are 6 second nearest neighbours in the crystal
The second nearest neighbour atoms will be the closest atoms that
not touch the atom at the origin