<div dir="ltr"><div>Hi,</div><div><br></div><div>I'm not very sure that this is correct, but I would say that what you're missing is time reversal symmetry (that indeed is not</div><div>listed in the output file because it is not a lattice-related symmetry): k <=> -k</div><div><br></div><div>[1/3,0,0] is equivalent to [1/3-1,0,0]=[-2/3,0,0] because they differ by a lattice translation</div><div>[-2/3,0,0] is equivalent to [2/3,0,0] (k <=> -k)</div><div>So, [1/3,0,0] is equivalent to [2/3,0,0]</div><div><br></div><div>In the attached image:</div><div>- blue hexagon: 1st BZ</div><div>- blue dot: Gamma</div><div>- orange dot: [1/3,0]</div><div>- red dot: [2/3,0]</div><div>- green dot: [-1/3,0]<br><br>Red is outside the 1st BZ, because it is equivalent to green (by a lattice translation).</div><div>Green in turn is equivalent to orange because k <=> -k</div><div><br></div><div>Giovanni</div><div><br></div><div><img src="cid:ii_m6z6f15g0" alt="image.png" width="520" height="537"><br></div><div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><span style="color:rgb(0,0,0)">-- <br><br>Giovanni Cantele, PhD<br>CNR-SPIN<br>c/o Dipartimento di Fisica<br>Universita' di Napoli "Federico II"<br>Complesso Universitario M. S. Angelo - Ed. 6<br>Via Cintia, I-80126, Napoli, Italy<br><a href="mailto:giovanni.cantele@spin.cnr.it" style="color:rgb(17,85,204)" target="_blank">e-mail: giovanni.cantele@spin.cnr.it</a><br>Phone: +39 081 676910<br>Skype contact: giocan74<br><br>ResearcherID: <a href="http://www.researcherid.com/rid/A-1951-2009" style="color:rgb(17,85,204)" target="_blank">http://www.researcherid.com/rid/A-1951-2009</a><br>Web page: </span><a href="https://sites.google.com/view/giovanni-cantele/home" style="color:rgb(17,85,204)" target="_blank">https://sites.google.com/view/giovanni-cantele/home</a><br></div></div></div><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">Il giorno lun 10 feb 2025 alle ore 14:13 Lukas Cvitkovich <<a href="mailto:lukas.cvitkovich@physik.uni-regensburg.de" target="_blank">lukas.cvitkovich@physik.uni-regensburg.de</a>> ha scritto:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><u></u>
<div>
<p>Dear QE users and developers,</p>
<p>I am currently trying to reproduce the construction of an
irreducible k-point set as done by QE. <br>
For this, I set "verbosity = high" to get the symmetry operations
printed in the output file. <br>
I start from a uniform k-point mesh. Then, using the same symmetry
operations as QE, I transform every k-point and fold it back in
the first Brillouin zone.<br>
If the resulting k-point falls on another k-point of the uniform
grid, it is NOT irreducible. <br>
In this manner, as also described by Blöchl et al (Phys. Rev. B <b>49</b>,
16223, 1994) I find the set of irreducible kpoints.<br>
</p>
<p>My code agrees with QE for a simple structure (fcc crystal tested
and verified) but I have problems with a more complicated case
(the 2D magnet FGT).<br>
In this example, 6 symmetry operations are found (see attached
QE-output file).<br>
Starting from a 3x3x3 uniform grid, the irreducible set of kpoints
- according to QE - contains 7 points. However, I find 12
irreducible k-points.<br>
</p>
<p>First, please note, that every point found by QE is also
contained in my set. But I find additional points which (according
to QE) should be related by some symmetry operation. By looking at
the weights, I could figure out which kpoints should belong
together. <br>
For instance: According to QE, the kpoints [1/3, 0, 0] and [2/3,
0, 0] are equivalent, as well as [0, 0, 1/3] and [0, 0, 2/3]
should be equivalent too. I recognized that all the extra points
could be transformed into each other by translating the lattice.
However, applying all the symmetry operations from the QE output
file (these are exclusively rotations and not translations), I
cannot transform these points into each other. You might try for
yourself.</p>
<p>So the question that I would like to ask is: Are there any
"hidden" symmetry operations which are not explicitly printed in
the output file? Could fractional translations be the reason? Is
it maybe related to differences between point group and space
group? Any other hints to what I am missing?</p>
Thank you! Your help would be highly appreciated!<br>
<br>
Best,<br>
Lukas
<p></p>
</div>
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