Question

In a CCP structure of compound XY, X atoms are present at ocathedral voids. Calculate the number of nearest neighbours upto 6th C.N. for an X atom located at body centre . plz explain this clearly with diagram..

Answer 1

Explanation:

In CCP the atom are in face centre and atom can also occupy tetrahedral void and octahedral void.

X atom is occupying the octahedral void and Y is occupying the face centre.

Let's assume eight unit cell. In the diagram, we can see that X is occupying the centre of the big cube. The six Y atom forms a octahedral shape around X. That is why X is said to be in octahedral void.

Coordination number of X is 6.

Coordination number is the number of atoms or ions immediately surrounding a central atom in a complex or crystal.

Let's assume, the length of the cube is 2a.

Consider the shaded red color square. The length between the X and Y is a, while length between X and another X is $\sqrt{2} a$. So the nearest would be Y atom. There are six Y atom around X atom thus the coordination number is 6.