[Wien] Supercell structure co-ordinates are different in Wien2k and PHON

[Fecher, Gerhard]

The 12 atoms cell is obviously not the P 1 (space group 1) but P m (space group 6) cell
I do not know why the supercell program keeps mirror operations. 
Is there a "wanted" or "necessary"  reason for this behaviour ?

It is easy to check that the P 1 cell contains 16 atoms (sgroup finds F m-3m with 8c, 4b, and 4a occupied).
(It seems that superstruct has a problem with the 8c position)

For Phonon calculations one would need the P 1 cell,
otherwise one moves (in certain cases)   2 or more atoms at once out of there equilibrium positions (here Fe atoms)

A workaround for the present case would be to start with the structure set up inm F -43m (216), in that case, superstruct delivers P 1 !


Ciao
Gerhard

DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
"I think the problem, to be quite honest with you,
is that you have never actually known what the question is."

====================================
Dr. Gerhard H. Fecher
Institut of Inorganic and Analytical Chemistry
Johannes Gutenberg - University
55099 Mainz
and
Max Planck Institute for Chemical Physics of Solids
01187 Dresden
________________________________________
Von: wien-bounces at zeus.theochem.tuwien.ac.at [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von venkatesh chandragiri [venkyphysicsiitm at gmail.com]
Gesendet: Mittwoch, 3. Dezember 2014 22:22
An: wien at zeus.theochem.tuwien.ac.at
Betreff: [Wien] Supercell structure co-ordinates are different in Wien2k and    PHON

Dear Sir,

I have planned to carry out the Phonon density of states analysis of alloy with a cubic structure. The initial structure file contains 12 atoms with a primitive type.Now, I have generated 2x2x2 supercell using the same struct file (contains 12 number of atoms) in both Wien2k and PHON programs. For Wien2k, depending on the selection of the output lattice (FCC, BCC, primitive), the number of atoms would change.

For primitive = 96 atoms, BCC = 48 atoms, FCC = 24 atoms.

In PHON, generation of 2x2x2 supercell gives SPOSCAR file that contained 48 atomic positions. Hence, I decided to use BCC output super cell stuct file generated from Wien2k for Force calculation. But, the generated positional co-ordinates are not matches with the PHON one for some of the atoms. Please, have a look of the both structure files attached to this mail. Now, I was stuck with which structure file have to use for Force minimization. Hence, kindly guide me to proceed further.

thanking you and looking forward to your reply

Sincerely,
Ch. Venkatesh,
C/o. Prof. V. Srinivas,
Department of Physics
IIT Madras