A crystal is made of particles X and Y. X for | vedclass

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(B) In an $fcc$ unit cell,the number of $X$ atoms at corners is $8 	imes \frac{1}{8} = 1$ and at face centers is $6 	imes \frac{1}{2} = 3$,so total

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$X_5Y_4$

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(B) In an $fcc$ unit cell,the number of $X$ atoms at corners is $8 	imes \frac{1}{8} = 1$ and at face centers is $6 	imes \frac{1}{2} = 3$,so total $X = 4$.The number of octahedral voids in $fcc$ is equal to the number of atoms,so total $Y = 4$.Along one body diagonal,there are $2$ corner atoms of $X$ and $1$ octahedral void of $Y$ (at the body center).Removing these particles:Number of $X$ atoms remaining $= 4 - (2 	imes \frac{1}{8}) = 4 - 0.25 = 3.75 = \frac{15}{4}$.Number of $Y$ atoms remaining $= 4 - 1 = 3$.The ratio $X:Y = \frac{15}{4} : 3 = 15 : 12 = 5 : 4$.Thus,the formula is $X_5Y_4$.

$A$ crystal is made of particles $X$ and $Y$. $X$ forms $fcc$ packing and $Y$ occupies all the octahedral voids. If all the particles along one body diagonal are removed,then the formula of the crystal would be:

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