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Calcium crystallises in a face-centred cubic unit cell with a=0.556nm.Calculate the density if it contained 0.1% Frenkel defects.

$\begin{array}{1 1}1.5455g/cm^3\\2.5455g/cm^3\\3.5455g/cm^3\\4.5455g/cm^3\end{array} $

1 Answer

Frenkel defects do not change the value of the theoretical density because the atom is only occupying an interstitial position instead of lattice position.
Thus density can be determined using
$a=0.556nm=0.556\times 10^{-9}m$
$\Rightarrow 0.556\times 10^{-7}cm$
$\rho$(with Frenkel defects)=$\large\frac{40\times 4}{6.023\times 10^{23}\times (0.556\times 10^{-7})^3}$
$\Rightarrow 1.5455g/cm^3$
answered Aug 1, 2014 by sreemathi.v

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