Question

In a unit cell, atoms A, B, C and D are present at half of total corners, all face-centres, body-centre and one third of all edge-centres respectively. Then formula of unit cell is ?

• A. $A{B}_{3}C{D}_3$
• B. ABCD
• C. $A{B}_6{C}_2{D}_4$
• D. $A{B}_6{C}_2{D}_2$

Answer 1

The correct option is D $A{B}_6{C}_2{D}_2$

Atoms at the corner in a unit cell is 1
No of atoms of A in one unit cell = $\frac{1}{2}$
Atoms at the corner in a unit cell is 3
No of atoms of B in one unit cell = 3
Atoms at the body center in a unit cell is 1
No of atoms of C in one unit cell = 1
Atoms at the edge center in a unit cell is 3
No of atoms of D in one unit cell = 1
Formula is $A_{\frac{1}{2}}{B}_{3}CDorA{B}_6{C}_2{D}_2$