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

[Gavin Abo]

See comments below.

here is correct inst configuration from attached struct file:
This configuration is uddu and not udud. Right?


The answer to the above question depends on how you define udud.  It is 
udud if you define it as follows.


For the "instgen_lapw -ask" input and case.inst below, you have Fe1 as 
up and Fe2 as down.  So you have specified ud configuration to the 
program.  As you should see in case.inst, there is only spin state 
blocks for each of the nonequivalent atomic positions as the WIEN2k 
program handles the duplicate atoms (equivalent atomic positions) for you.


So for the structure, you have specified (for the positions seen in your 
case.struct):


Fe1 nonequivalent atomic position: X=0.3334 Y=0.6668 
Z=0.5000 (up spin)
     - Fe1 equivalent atomic position: X=0. Y=0.3332 
Z=0.  (up spin)


Fe2 nonequivalent atomic position: X=0.3334 Y=0.6668 
Z=0.30898400 (down spin)
     - Fe2 equivalent atomic position: X=0. Y=0.3332 
Z=0.80898400 (down spin)


So you have udud configuration for your structure with position(1/3, 
2/3, 1/2) as up, (1/3, 2/3, 0.308984) as down, (2/3, 1/3, 0) as up, and

(2/3, 1/3, 0.808984) as down.

If it is uddu configuration then please guide me how to get udud 
configuration (I can switch the spin manually but I just want to be 
sure that why I am not getting from instge_lapw -ask).


generate atomic configuration for atom 4 : Fe1
select spinpolarization up, dn or non-magnetic ( u, d, n )
u
..
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
4,-1,0.5  N



generate atomic configuration for atom 8 : Fe2
select spinpolarization up, dn or non-magnetic ( u, d, 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
4,-1,1.0  N







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

[Gavin Abo]

With instgen_lapw, you specify just ud or dn in that case as you have 
two nonequivalent positions.  Thus, only the one u and one d that you 
see in case.inst.  However, you have a multiplicity of 2 for each of the 
two nonequivalent positions.  So one of the nonequivalent Fe positions 
corresponds to two atoms with uu.  The dd comes from the second 
nonequivalent position.  In total, when you arrange the uu from the 
first two Fe atoms and dd from the second two Fe atoms that gives you an 
udud configuration.



On 8/23/2018 5:20 AM, Enamul Haque wrote:

Dear Sir,
We get SG  8 Cm if we run sgroup with "x sgroup -settol .0100".

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 Haque
Mawlana Bhashani Science and Technology University
Tangail, Bangladesh.
Email: ena...@mailaps.org
Cell: +8801831911133
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Re: [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 90.00 90.00120.00
ATOM   1: X=0.6733 Y=0.3267 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 90.00 90.00125.517869
ATOM   1: X=0.26213500 Y=0.92880100 Z=0.

 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 90.00 90.00120.00


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: ena...@mailaps.org 
Cell: +8801831911133



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--

  P.Blaha
--
Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300 FAX: +43-1-58801-165982
Email: bl...@theochem.tuwien.ac.atWIEN2k: http://www.wien2k.at
WWW:   http://www.imc.tuwien.ac.at/TC_Blaha
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