Question

Edge length of FCC unit cell is 400 A0 .Find radius of atom

Answer 1

Explanation:

Remember that a face-centered unit cell has an atom in the middle of each face of the cube. The square represents one face of a face-centered cube:

Applying Pythagoras theorem,

a

2

+a

2

=(r+2r+r)

2

⇒

2

⏩ a=4r

Answer 2

Answer:

Explanation:

In FCC: The atoms at the face diagonals touch each. If a is the edge length of cube and r is the radius of the atom.

So,  

2

​  

a=4r

⇒a=2  

2

​  

r

In bcc: The atoms at the body diagonal touch each other.

So,  

3

​  

a=4r

⇒a=  

3

​  

 

4

​  

r

In simple cubic: The atoms at the corners touch each other.

So, a=2r