o
o
o
These voids are called tetrahedral voids because a joining of the centers of four spheres gives rise to tetrahedron.
There are areas where the triangular voids in the second layer lies above the triangular voids of the first layer, and the triangular shapes of these do not overlap.
One of them has the apex of the triangle pointing upwards and the other downwards.
o
Such voids are surrounded by six spheres and are called octahedral voids( O).
Let the number of close packed spheres be N, then: The number of octahedral voids generated in the structure = N. The number of tetrahedral voids generated in the structure = 2N.
Question: If the radius of the octahedral void is r and radius of the atoms in close packing is R, derive relation between r and R.
Answer: Given that Radius of octahedral void in close packing = r Radius of atom in close packing = R Using Pythagoras theorem, 2R 2 =( R + r) 2 +( R + r) 2