Question

The number of octahedral voids in CCP unit cell
whose contribution towards unit cell is 1/4​

Answer 1

Given,

contribution of voids towards unit cell is 1/4.

To find,

The number of octahedral voids in ccp unit cell whose contribution towards unit cell is 1/4.

octahedral voids are located at edge centres of unit cell and also one octahedral void is located at the very centre of cubic close packing (ccp or facc).

we know, atom placed at edge centre is shared by 4 other unit cell. so here indirectly question ask to find us number of octahedral voids which are placed at edge centres of unit cell.

now tell me number of edges of a cube ??

of course, 12 edges and each edge is shared by 4 other cube. so, number of octahedral voids = 12/4 = 3

Therefore there are three octahedral voids whose contribution towards unit cell is 1/4