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Trying to answer your comments;</div>
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SG227 is FCC, that is, the conventional cell has 4 primitive cells</div>
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the first wyckoff positions are;</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
8a 1/8,1/8,1/8<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"></span><br>
<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">8b 3/8,3/8,3/8</span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><br>
</span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">16c 0,0,0</span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">16d 1/2,<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">1/2,<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">1/2</span></span></span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><br>
</span></span></span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">32e
x,x,x</span></span></span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><br>
</span></span></span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">8a
and 8b have 2 atoms in the primitive cell</span></span></span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">16c
and 16d have 4</span></span></span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">32e
has 8</span></span></span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><br>
</span></span></span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">MnFe2O4
is a spinel</span></span></span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">Mn;
8a</span></span></span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">Fe;
16d</span></span></span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">O;
32e x=0.2639</span></span></span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">The
primitive cell has 2 formula units while the conventional cel has 8 formula units<br>
</span></span></span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"> </span></span></span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span><span>then
the atomic positions in <span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">
<span><span>MnFe2O4</span></span></span>.struct are;<br>
</span></span></span></span></span></span></div>
F LATTICE,NONEQUIV.ATOMS: 3 227_Fd-3m
<div><br>
</div>
<div> 16.059466 16.059466 16.059466 90.000000 90.000000 90.000000</div>
<div><br>
</div>
<div>ATOM 1: X=0.12500000 Y=0.12500000 Z=0.12500000</div>
<div>ATOM 1:X= 0.87500000 Y=0.87500000 Z=0.87500000</div>
<div>Mn NPT= 781 R0=0.00005000 RMT= 1.8600 Z: 25.000</div>
<div><br>
</div>
<div>ATOM -2: X=0.50000000 Y=0.50000000 Z=0.50000000</div>
<div>ATOM -2:X= 0.50000000 Y=0.75000000 Z=0.75000000</div>
<div>ATOM -2:X= 0.75000000 Y=0.75000000 Z=0.50000000</div>
<div>ATOM -2:X= 0.75000000 Y=0.50000000 Z=0.75000000</div>
<div>Fe NPT= 781 R0=0.00005000 RMT= 2.1500 Z: 26.000</div>
<div><br>
</div>
<div>ATOM -3: X=0.26390000 Y=0.26390000 Z=0.26390000</div>
<div>ATOM -3:X= 0.73610000 Y=0.73610000 Z=0.73610000</div>
<div>ATOM -3:X= 0.73610000 Y=0.51390000 Z=0.51390000</div>
<div>ATOM -3:X= 0.26390000 Y=0.98610000 Z=0.98610000</div>
<div>ATOM -3:X= 0.98610000 Y=0.98610000 Z=0.26390000</div>
<div>ATOM -3:X= 0.51390000 Y=0.51390000 Z=0.73610000</div>
<div>ATOM -3:X= 0.51390000 Y=0.73610000 Z=0.51390000</div>
<div>ATOM -3:X= 0.98610000 Y=0.26390000 Z=0.98610000</div>
<div>O NPT= 781 R0=0.00010000 RMT= 1.6000 Z: 8.000</div>
<br>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
Now, if one wants to make it antiferro then one posibility is to take two Fe 'up' and two 'dn', and the system becomes;</div>
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<br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
B LATTICE,NONEQUIV.ATOMS: 5 74_Imma
<div><br>
</div>
<div> 11.355757 11.355757 16.059466 90.000000 90.000000 90.000000</div>
<div><br>
</div>
<div>ATOM 1: X=0.00000000 Y=0.25000000 Z=0.12500000</div>
<div>ATOM 1:X= 0.00000000 Y=0.75000000 Z=0.87500000</div>
<div>Mn NPT= 781 R0=0.00005000 RMT= 1.8600 Z: 25.000</div>
<div><br>
</div>
<div>ATOM 2: X=0.25000000 Y=0.75000000 Z=0.25000000</div>
<div>ATOM 2:X= 0.25000000 Y=0.25000000 Z=0.75000000</div>
<div>Fe1 NPT= 781 R0=0.00005000 RMT= 2.1500 Z: 26.000</div>
<div><br>
</div>
<div>ATOM 3: X=0.00000000 Y=0.52780000 Z=0.26390000</div>
<div>ATOM 3:X= 0.00000000 Y=0.47220000 Z=0.73610000</div>
<div>ATOM 3:X= 0.00000000 Y=0.02780000 Z=0.73610000</div>
<div>ATOM 3:X= 0.00000000 Y=0.97220000 Z=0.26390000</div>
<div>O 1 NPT= 781 R0=0.00010000 RMT= 1.6000 Z: 8.000</div>
<div><br>
</div>
<div>ATOM 4: X=0.77780000 Y=0.75000000 Z=0.48610000</div>
<div>ATOM 4:X= 0.22220000 Y=0.25000000 Z=0.51390000</div>
<div>ATOM 4:X= 0.77780000 Y=0.25000000 Z=0.51390000</div>
<div>ATOM 4:X= 0.22220000 Y=0.75000000 Z=0.48610000</div>
<div>O 2 NPT= 781 R0=0.00010000 RMT= 1.6000 Z: 8.000</div>
<div><br>
</div>
<div>ATOM 5: X=0.00000000 Y=0.00000000 Z=0.50000000</div>
<div>ATOM 5:X= 0.00000000 Y=0.50000000 Z=0.50000000</div>
<div>Fe2 NPT= 781 R0=0.00005000 RMT= 2.1500 Z: 26.000</div>
<br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
As it can be seen the 8 O atoms in 32e position are now in two groups of 4 O atoms</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
and as I mentioned before the 'runsp -min' will move them in a way that it would break the cubic FCC crystal symmetry.</div>
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The problem is that Fe in this system has the kagome arangement and antiferro ordering is just a simplification, but the system should be cubic with the SG 227.</div>
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<br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
Saludos</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
Pablo<br>
</div>
<hr tabindex="-1" style="display:inline-block; width:98%">
<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" color="#000000" face="Calibri, sans-serif"><b>De:</b> Wien <wien-bounces@zeus.theochem.tuwien.ac.at> en nombre de Fecher, Gerhard <fecher@uni-mainz.de><br>
<b>Enviado:</b> martes, 2 de noviembre de 2021 05:07 a. m.<br>
<b>Para:</b> A Mailing list for WIEN2k users <wien@zeus.theochem.tuwien.ac.at><br>
<b>Asunto:</b> Re: [Wien] Optimization of an spinel structure</font>
<div> </div>
</div>
<div class="BodyFragment"><font size="2"><span style="font-size:11pt">
<div class="PlainText">Sorry,<br>
it depends on the setting for space group 227 whether X=1/4 results in a 8- or 32-fold degenerate position, I did not check which one Wien2k uses (unfortunately one can not use crystallographic Wykoff positions directly).<br>
if you have already the 32-fold degenerate site (I guess wien2k reports a smaller cell with 8 sites) then min should find the correct positions by minimizing the forces.<br>
<br>
The remarks on the magnetic order are not touched by that.<br>
<br>
Ciao<br>
Gerhard<br>
<br>
DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:<br>
"I think the problem, to be quite honest with you,<br>
is that you have never actually known what the question is."<br>
<br>
====================================<br>
Dr. Gerhard H. Fecher<br>
Institut of Physics<br>
Johannes Gutenberg - University<br>
55099 Mainz<br>
________________________________________<br>
Von: Wien [wien-bounces@zeus.theochem.tuwien.ac.at] im Auftrag von delamora [delamora@unam.mx]<br>
Gesendet: Dienstag, 2. November 2021 04:49<br>
An: wien@zeus.theochem.tuwien.ac.at<br>
Betreff: [Wien] Optimization of an spinel structure<br>
<br>
Dear WIEN community,<br>
I am trying to optimize a spinel structure.<br>
The normal spinel AB2X4 is FCC with SG 227<br>
A: 1/8,1/8,1/8<br>
B: 1/2,1/2,1/2<br>
X: x,x,x x~1/4<br>
so it has 2 free parameters; 'volume' and 'x,x,x'<br>
but in my cases B is magnetic and it has antiferromagnetic coupling, B also forms the 3D Kagome structure so it is geometrically frustrated.<br>
The volume optimization can be easily done with option 'optimize'<br>
but for the 'x' parameter there is a problem;<br>
To treat the magnetism the best option, in my opinion, is to put half of the B atoms 'up' and the other half 'dn', there are 4 in the primitive cell, so 2 are 'up' and 2 'dn'.<br>
With this, then the FCC cell becomes BCC (SG 74 Imma) and the 8 'X' atoms that were in one wyckoff position are now in two wyckoff positions with 4 atoms in each.<br>
So, if the forces are minimized, 'runsp -min', will move these two 'X' groups in directions that will break the original cubic symmetry.<br>
One posibility is to make 4 'struct' files, in the original SG 227, with slightly different 'x' positions, for example, the initial x,x,x is;<br>
x= 0.254, so I make 4 struct files with; 0.251, 0.253, 0.255, 0.257<br>
after this one should make them antiferromagnetic (SG 74 Imma) then run them separatelly, then one can obtain the optimum 'x' parameter.<br>
<br>
I tried to use a modified 'optimize.job' but it did not work.<br>
I also tried to run these 4 'struct' files in the same directory but I found that when I put the next case.struct into the directory, I had to initiate the system in order to be able to run them.<br>
<br>
In other words, if I run the system with 1-struct, then for the next 2-struct I cannot just change 1-struct for 2-struct and run.<br>
For the case of changes of volume then the optimize.job works fine, but for small changes in 'x' it does not work.<br>
<br>
I anybody has an idea that would make this case simpler I would apreciate.<br>
Thank you anyway<br>
<br>
Pablo<br>
<br>
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