00:01
In this question, for fcc lattice, that is face -centered cubic crystalline structure, we have to derive a relation between a, that is, edge length, as well as r, that is, atomic radius.
00:13
So, we have a cube with edge length a and radius r of a atom.
00:20
Now, since it is fcc, so atoms are present at the centers of the corners, as well as at corners, as well as the corners, as well as the face centers.
00:31
So if we put that atoms at the corners, so one atom at the corner, another at the face center and another atom at a corner.
00:42
We can see that there is a three atom which are aligned to each other in a straight line.
00:49
So this is the phase diagonal.
00:52
Now let's mark this as b and these three triangle vertices are a, b and c...