a) what is the stoichiometry of Y:Ba:O:Cu? I think the answer to this is 1:2:3:7

Question

a) what is the stoichiometry of Y:Ba:O:Cu?

I think the answer to this is 1:2:3:7

b) What is the coordination number of the Y3+? What type of hole does it occupy?

I think CN=6 and occupies octahedral hole.

c) If you assume that every ion in the cell is O2-, what is the packing fraction of the cell?

The length of one short side is 3.8227 A and long side is 11.6802 A. (I'm not sure if this information is relevant)

I'm pretty sure of a) but please explain b) and c) even if I was right!! Thank you.

Explanation / Answer

a) stoichiometry of Y:Ba:O:Cu will be 1:2:7:3 . Remember, position of O and Cu are reversed in ratio. You missed it!!!

b) coordination number = 6

Share by O= 8*0.5 = 4, share by Cu = 8*0.25 = 2

so coordination number = 2+4 = 6

c) Packing fraction = volume of all atoms/[3.8227*3.8227*11.6802]

                = (4/3 pi)* [7*1.55^3+3*1.28^3+2*2.7^3+1*2.12^3]/[3.8227*3.8227*11.6802]

              = 0.202

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