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Calcium crystallizes in fcc unit cell wi...

Calcium crystallizes in fcc unit cell with `0.556 nm`. Calculate the density if
a. It contains `0.2%` Frenkel defects
b. It contains `0.1%` Schottky defects

Text Solution

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(i) Density in case of Frenkel defects. The Frenkel defects do not change the density because the number of atoms Per unit cell remains the same.
`rho=(ZxxM)/(a^(3)xxN_(0))=(4xx("40 g mol"^(-1)))/((0.556xx10^(-7)cm)^(3)xx(6.022xx10^(23)"mol^(-1)))`
`=1.5463"g cm"^(-3)`
(ii) Density in case Schottky defects. Due to Schottky defects, vacant spaces will decrease the number of atoms per unit cell.
`therefore" "Z=(4-(4xx0.1)/(100))=3.996`
`rho=(ZxxM)/(a^(3)xxN_(0))=((3.966)xx("40 g mol"^(-1)))/((0.556xx10^(-7)cm)^(3)xx(6.002xx10^(23)mol^(-1)))`
`=1.5448"g cm"^(-3)`
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