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

[Peter Blaha]

 From the files you sent, I never get Cm space group.

Anyway, if it is antiferromagnetic, it has only TWO Fe sites, one with 
spin-up and one with dn.

So I used your struct file, but the 4 Fe atoms should probably not be 
splitted into 1-4, but into two positions, each with multiplicity 2, 
such that you get the desired udud spin-pattern.

sgroup gives then P63mc.

PS: You have to distinguish between a hexagonal bravais lattice 
(aac,90,90,120) and a hexagonal space group. If you have a hexagonal 
lattice, but put atoms in in an arbitrary way, it can easily even go to 
P1. So the lattice is still hexagonal, but the SG does not belong to a 
hexagonal SG, since the required symm.ops of a hex.SG are gone.

On 08/20/2018 02:54 PM, Enamul Haque 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 Haque
> Mawlana Bhashani Science and Technology University
> Tangail, Bangladesh.
> Email: enamul at mailaps.org <mailto:enamul at mailaps.org>
> Cell: +8801831911133
> 
> 
> 
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
> SEARCH the MAILING-LIST at:  http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
> 

-- 

                                       P.Blaha
--------------------------------------------------------------------------
Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
Email: blaha at theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
WWW:   http://www.imc.tuwien.ac.at/TC_Blaha
--------------------------------------------------------------------------