[Wien] problem regarding supercell

[Pooja Rana]

Respected Prof. Blaha and dear WIEN2K users,

Presently I am trying to define a supercell  for Na(1-x) K(x) Cl type of 
compound with fcc structure (225 Fm-3m). But I am able to create the supercell 
but unable to define impurity position and composition ( x= 0.05, 0.1, 0.15, 
0.2, .... ). 

If I  define the structure for Na and Cl only and created a supercell of 8 atoms 
and introduce an impurity in one of the Na atom then it gives error  " atom #1 
and atom #3 coincide".

Should I  define three atoms  for Na , K, Cl simulatanoeusly during the 
structure generation with positions of Na , K, Cl ?
When I did so, I got error in dstart "unit 15 ( case.in2c) can not be opened".

Regards and thanks,

 Pooja Rana 
Research Scholar 
Condensed Matter Theory Group 
School of Studies In Physics 
Jiwaji University, GWALIOR - 474011 (M.P.), INDIA
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