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please justify your answer with a diagram and explanation. A hypothetical compou

ID: 1021315 • Letter: P

Question

please justify your answer with a diagram and explanation.

A hypothetical compound with formula AB_2O_4 adopts an FCC crystal structure where O^2- ions form the lattice points. A^2+ ions are only located in octahedral voids, while B^2+ ions are distributed equally between tetrahedral and octahedral voids. calculate the fraction of octahedral and tetrahedral voids occupied? For you information octahedral sites in FCC are 1/2 1/2 1/2 and family of 0 0 1/2; while tetrahedral sites include family of 1/4 1/4 1/4

Explanation / Answer

In FCC

there are 4 lattice point

There are 4 octahedral voids

there are 8 tetrahedral voids

O2- takes all 4 lattice point

A2+ takes 1 octahedral void

B2+ takes 1 octahedralvoid and 1 tetrahedral void

octahedral void occupied = 2

tetrahedral void occupied = 1

fraction of octahedral void occupied = 2/4 = 1/2

fraction of tetrahedral void occupied = 1/8