Question

1.The no. of carbon atoms per unit cell of diamond unit cell is
(A) 8
(B) 6
(C) 1
(D) 4

Answer 1

option A) 8

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Answer 2

Diamond unit cell is F.C.C type with four additional C atoms tetrahedrally bonded(black ones). Corner aoms contributes to 1/8th of the atom to the unit cell , Face centred atoms contributes 1/2 of the atom .Now, Total atom in one cell can be summed up to :

(1/8 X 8) +(1/2 X 6) + 4(tetrahedrally bonded atoms in the cell) = 8.