[QE-users] "non-stoichiometric unit cell"

[Tarek Hammad]

Dear users and QE team

I have tried to perform DFT calculations on Zn3P2 compound,namely, the 
"orthorhombic" high pressure phase with space_group #59 pmmn.

To do that, I introduced the lattice parameters and atomic positions and 
other information taken from literature data to Bilbao structure 
converter utility.

This return back CIF file which I used it. However, I found that the 
obtained unit cell contains 24 atoms, 16 for Zn and 8 for P atoms!! But 
this violate the ratios of Zn to P atoms according to the formula Zn3 P2 
!!!.

Neverthless, I ran scf calculations successfully but for me this is not 
everything. So, would you help me please?

Thanks a lot in advance.

Kind regards

Dr. Tarek Hammad.