The CORRECT statement(s) for cubic close packed (ccp) three...

The CORRECT statement(s) for cubic close packed (ccp) three dimensional structure is (are)

Options

AThe number of the nearest neighbours of an atom present in the topmost layer is 12
BThe efficiency of atom packing is $74%$
CThe number of octahedral and tetrahedral voids per atom are 1 and 2, respectively
DThe unit cell edge length is $2\sqrt{2}$ times the radius of the atom

Correct answer

B. The efficiency of atom packing is $74%$

Step-by-step solution

CCP is ABC ABC ..... type packing
A] In topmost layer, each atom is in contact with 6 atoms in same layer and 3 atoms below this layer.
B] Packing fraction

= \dfrac{4 \times \dfrac{4}{3}\pi{r}^{3}}{{\left(\dfrac{4r}{\sqrt{2}}\right)}^{3}} = \left(0.74\right)

C] Each FCC unit has effective no of atoms = 4
Octahedral void = 4
Tetrahedral void = 8
D]

4r = a\sqrt{2}

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