When I tried to count, I found 24 tetrahedral voidsholes (each formed by 2 body centers of 2 unit cells sharing a face and 2 vertices of the same edge of that face).As As each voidhole is being shared by 2 unit cells, there are 12 voidsholes per unit cell. Does it mean that it defies the rule that there are 2*n tetrahedral voids for n packed spheres(because bcc has 2 atoms effectively pr uni cell.It should have had only 4 tetrahedral voids then). Or is this process wrong?
Also,I found 6 octahedral voidsholes (6 at face centers being shard by 2 unit cells each and 12 at every edge center being shared by 4 unit cells each).
Generally I was taught that for $n$ packed spheres, there should be $2n$ tetrahedral holes. Does the analysis above mean that this rule doesn't apply here?