[Pw_forum] How to select unit cell for optimization calculation?

[Youssef]

Dear Max,

You can use the following 14 atoms coordinates for spinel AB2O4 (fd-3m 
origin choice 2), replace "x" with oxygen parameter from 32e wykoff 
site (0.2627 for your case)

A	 0.125	 0.125	 0.125
A	 0.875	 0.375	 0.375
B	 0.5	 0.5	 0.5
B	 0.25	 0.75	 0
B	 0.75	 0	 0.25
B	 0	 0.25	 0.75
O	 (x)	 (x)	 (x)
O	 (1.25-x)	 (x+0.5)	 (1.75-x)
O	 (x+0.75)	 (x+0.25)	 (1.5-x)
O	 (x+0.25)	 (1.5-x)	 (1.75+x)
O	 (1.75-x)	 (1.25-x)	 (x+0.5)
O	 (x+0.5)	 (1.75-x)	 (1.25-x)
O	 (1-x)	 (1-x)	 (1-x)
O	 (1.5-x)	 (x+0.75)	 (x+0.25)


to be used with  ibarv = 2 and ATOMIC_POSITIONS alat (not crystal) , I 
didn't test it in QE, please confirm if it works!

Youssef Aharbil,
Laboratory of Physics and Chemistry of Materials
Faculty of sciences Ben msik, Casablanca
Morocco
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