Calculate the packingeffeciency of a fcc crystal in which all the tetrahedraland octahedral voids are occupied by the largest spheres withoutdisturibing thelattice.

Calculate the packingeffeciency of a fcc crystal in which all the tetr

1.	Calculate the packingeffeciency of a fcc crystal in which all the tetrahedraland octahedral voids are occupied by the largest spheres withoutdisturibing thelattice.
Answer» SOLUTION :FCC has 4 atoms per unit cell No. of tetrahedral voids = 8 No. of octadedral VOILDS = 4 If Ris theradius of the atoms in the packing Radius of tetahedral void = 0.225 R RADIUSOF octahedral void = 0.414 R for fcc,` a = 2 sqrt2 r = 2sqrtR` packing efficiency` = (" Volume occupied by allspheres")/("Volume of the unit cell") ` ` = (4 xx 4/3 PI R^(3)+ 8 xx 4/3pi ( 0.225 R)^(3) + 4 xx 4/3 pi ( 0.414 R)^(3))/((2sqrt2R)^(3))`= 0.81