[Wien] primitive cell for PHON

[venkatesh chandragiri]

Dear Sir,

I am planing to carryout phonon calculations using PHON package.  For this,
I need to generate the primitive structure of the given material which is
going to fed into PHON program. In wien2k, one could able to generate the
structure file by giving atomic co-ordinates and space group. In xcrysden,
one could press F3 and F4 to toggle between the primitive and conventional
cell types. After this, I have extracted the case.struct from xcrysden when
it is showing primitive cell mode.

Later, I have uploaded this case.struct into another package called VESTA
to check the actual primitive cell. This case.struct results a structure
looks like conventional cell with FCC type  with space group 1 (actual
space group, 225 was not shown).

In PHON code, I have to give the primitive cell of the given material in a
POSCAR format (this is the structure file in VASP program). For this, I
have used same VESTA package to save this primitive cell data into VASP
format (POSCAR file). But, the program VESTA saved it as 16 number of
co-ordinates with a cubic type (not a 4 co-ordinates with FCC type). The
phonon calculations will take much more time if i could use this 16
numbered POSCAR and the time consumption may be greatly reduced, if i could
use the 4 numbered FCC type POSCAR file. Hence, kindly suggest me the
proper pathway to get the POSCAR of FCC type using wein2k-4 atomic
primitive cell sturct generated by xcrysden. kindly, find the attached
struct files in the various formats for your reference.

My compound was Fe2VAl with a 225 space group, F m-3m symmetry

Fe (0.25,0.25,0.25)
V (0.5,0.5,0.5)
Al (0,0,0)

I need your suggestions to proceed further,

thanking you and looking for your help.

Sincerely,
venkatesh chandragiri

C/o. Prof. V. Srinivas,
Dept. of Physics
IIT Madras, INDIA.
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