• Let A in (1/8,1/8,1/8), B in (1/2,1/2,1/2) and O in (0.254,0.254,0.254)

I calculated F311 = -4( sqrt(2) FA + 6FB ) +0.606 FO

• If one assume that O is located in (0.25,0.25,0.25), the oxygen contribution vanishes :

F311 = -4( sqrt(2) FA + 6FB )

I did my calculation considering a spinels type structure (i.e. AB2O4 with a Fd-3m space group (227)).

If you assume A in (0,0,0) and B in (1/2,1/2,1/2), they will have same wyckoff multiplicity  leading to something which is not a spinel structure.

Dear Sir

Thank you for your answer.

I assumed that A in (0,0,0) and B in(5/8,5/8,5/8).

What is the influence of this on the form of the structure factor equations?

I do not have a suitable reference about the subject.

Thank you.

I'm sorry, I have made a mistake in my computation :

• Let A in (1/8,1/8,1/8), B in (1/2,1/2,1/2) and O in (0.254,0.254,0.254)

I calculated F311 = -4( sqrt(2) FA + 2FB ) +0.404 FO

• If one assume that O is located in (0.25,0.25,0.25), the oxygen contribution vanishes :

F311 = -4( sqrt(2) FA + 2FB )

• Your atomic positions are given in choice 1 of the space group (origin at -43m) but it doesn't change the result

Choice 1 choice 2

0,0,0 (8a)   1/8,1/8,1/8 (8a)

5/8,5/8,5/8 (16d) 1/2,1/2,1/2 (16d)