[Wien] Help me to solve #194 SG perovskites structure in AFM phase calculation problem

[Enamul Haque]

Dear Sir,We get SG  8 Cm if we run sgroup with "x sgroup -settol .00000100".
Anyway, now we are convinced with SG P63mc which belongs to the hexagonal family.
>From the new structure file (two Fe sites with multi. 2) we got below case.inst file but I am not able to get the point "how I can decide udud configuration" from this case.inst file?.................
Fe
Ar 3  
3, 2,2.0  N
3, 2,2.0  N
3,-3,2.5  N
3,-3,0.0  N
4,-1,1.0  N >>> u
4,-1,0.5  N >>> d
........................Fe
Ar 3  
3, 2,2.0  N
3, 2,2.0  N
3,-3,0.0  N
3,-3,2.5  N
4,-1,0.5  N  >> d
4,-1,1.0  N >>> u
****
****         END of input (instgen_lapw)


Best Regards,
Enamul HaqueMawlana Bhashani Science and Technology UniversityTangail, Bangladesh.Email: enamul at mailaps.orgCell: +8801831911133 

    On Monday, August 20, 2018, 6:54:50 PM GMT+6, Enamul Haque <enamul at mailaps.org> wrote:  
 
 Dear Wien2k Users and Experts,

We already got sufficient help from Dr. Gavin in this case but we are not convinced from the space group point of view.
With the original CIF file (attached), we want to check the ground state energy of the AFM case of "Cs3Fe2Cl9" (conventional standard and symmetrized taken from MP).
The original structure crystallizes in hexagonal space group (194) with one Fe atom having multiplicity 4. 

So to do AFM calculations, we need four Fe atoms (udud configuration is reported as a stable structure in AFM case).
We adopted two different ways to make four equivalent Fe atoms (to make udud AFM configuration) and in both the ways our space group adopts different geometry (SG) which does not fall within the hexagonal family.
Original SG:

H   LATTICE,NONEQUIV.ATOMS:  5 194 P63/mmc
MODE OF CALC=RELA unit=bohr
 14.141194 14.141194 34.315650 90.000000 90.000000120.000000
ATOM   1: X=0.66666733 Y=0.33333267 Z=0.41670700

Labeling all Fe (1-4) in the file we get from cif2struct from conventional standard cif file:

blebleble
CXZ LATTICE,NONEQUIV.ATOMS: 22 8 Cm
MODE OF CALC=RELA unit=bohr
 24.493266 42.160217 14.141194 90.000000 90.000000125.517869
ATOM   1: X=0.26213500 Y=0.92880100 Z=0.00000000

>From the supercell approach (from the symmetrized cif file after rounding off for two positions of Cl, ending with 50 and 800):

 
 1. initialize (it should be in 194 SG) 2. x supercell (1x1x1 with no shift) 3. cp case_super.struct case.struct 4. open in w2web and split one Fe and save it and it will redirect you again on w2web 5. hit edit structure option and again click on second Fe to split and split all four Fe atoms 6. again click on edit structure and put 1-4 on all four Fe atoms (in the second column) and remove original Fe atom (you see now five Fe atoms four that you have split and one will still on original position. So delete the original one). 
It gave us (attached case.struct)

H   LATTICE,NONEQUIV.ATOMS: 16 156 P3m1
MODE OF CALC=RELA unit=bohr
 14.141194 14.141194 34.315650 90.000000 90.000000120.000000


Now the issue we are facing is:The pristine structure is having SG 194 and after converting multiplicity of Fe atom to single atomic positions by two different approaches, we are getting two different SGs which do not fall within the hexagonal family.

So, Could someone from the expert list please advice us how to do AFM calculations of this kind cases and which SG should be appropriate.It will be a great help.




Best regards.
Enamul HaqueMawlana Bhashani Science and Technology UniversityTangail, Bangladesh.Email: enamul at mailaps.orgCell: +8801831911133
  
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