Question

what is the distance b/t 2 T.H.V. in F.C.C. unit cell?​

Answer 1

Answer:

The distance between any two successive (adjacent) tetrahedral voids. To calculate it, draw a line joining a tetrahedral void to the corresponding vertex. We know that this distance is 3√a4, now take the projection of this on any of the edges. The angle between body diagonal and an edge is cos inverse of 13√, so the projection of the line on an edge is a/4, Similarly the other tetrahedral void will also be a/4 away from its vertex on this edge. So the distance between these two is a−a/4−a/4=a/2