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<p>Let's assume there are two sheets of graphene: sheet 1 and sheet
2. If sheet 1 is place at a fixed position but sheet 2 is placed
directly above it in the z direction and then rotated around the z
axis with an angle Theta. Perhaps this is one definition of a
twisted angle (Theta).</p>
<p>In other words, similar to what is seen in Figure 1 of the
article "Twisted Bilayer Graphene: Interlayer Configuration and
Magnetotransport Signatures" at the link:<br>
</p>
<p><a class="moz-txt-link-freetext" href="https://doi.org/10.1002/andp.201700025">https://doi.org/10.1002/andp.201700025</a><br>
</p>
<p>And similar to FIG. 1b and FIG. 4b in the article "Gap Opening in
Twisted Double Bilayer Graphene by Crystal fields" at the link:<br>
</p>
<p><a class="moz-txt-link-freetext" href="https://arxiv.org/abs/1910.10524v2">https://arxiv.org/abs/1910.10524v2</a><br>
</p>
<p>If that is the case, it seems like it would be a matter of
geometry on how you would have to define your structure in
case.struct.</p>
<p>It looks like such a structure with two sheets would require
2D-slabs with 2 layers separated by a vacuum. <br>
</p>
<p>WIEN2k has tools such as "x supercell" and "structeditor" that
can help define 2D-slabs.</p>
<p>There is information in the mailing list archive [
<a class="moz-txt-link-freetext" href="http://susi.theochem.tuwien.ac.at/reg_user/mailing_list/">http://susi.theochem.tuwien.ac.at/reg_user/mailing_list/</a> ] and on
the Internet for these tools. A few examples are as follows.<br>
</p>
Slides 5-8:
<a class="moz-txt-link-freetext" href="http://susi.theochem.tuwien.ac.at/onlineworkshop/PB-getting_started3.pdf">http://susi.theochem.tuwien.ac.at/onlineworkshop/PB-getting_started3.pdf</a><br>
Slides 11-14 (Exercise 4):
<a class="moz-txt-link-freetext" href="http://susi.theochem.tuwien.ac.at/events/ws2015/Exercises_15.pdf">http://susi.theochem.tuwien.ac.at/events/ws2015/Exercises_15.pdf</a><br>
<a class="moz-txt-link-freetext" href="http://susi.theochem.tuwien.ac.at/reg_user/faq/supercells.html">http://susi.theochem.tuwien.ac.at/reg_user/faq/supercells.html</a><br>
<a class="moz-txt-link-freetext" href="http://wien2k-algerien1970.blogspot.com/2019/01/practising-supercell-tool.html">http://wien2k-algerien1970.blogspot.com/2019/01/practising-supercell-tool.html</a><br>
<a class="moz-txt-link-freetext" href="https://wien2k-algerien1970.blogspot.com/2017/12/how-to-create-slab-structure-2d-of.html">https://wien2k-algerien1970.blogspot.com/2017/12/how-to-create-slab-structure-2d-of.html</a>
<p>Section "9.29 structeditor" in the WIEN2k 19.1/19.2 usersguide
[<a class="moz-txt-link-freetext" href="http://www.wien2k.at/reg_user/textbooks/usersguide.pdf">http://www.wien2k.at/reg_user/textbooks/usersguide.pdf</a> ] has
"rotateatomlist" that you can read about that could of be interest
for this.<br>
</p>
<p>Another tool that has been used by others is VESTA [
<a class="moz-txt-link-freetext" href="https://jp-minerals.org/vesta/en/">https://jp-minerals.org/vesta/en/</a> ]:</p>
<p><a class="moz-txt-link-freetext" href="https://wien2k-algerien1970.blogspot.com/2017/12/how-to-construct-graphene-structure-and.html">https://wien2k-algerien1970.blogspot.com/2017/12/how-to-construct-graphene-structure-and.html</a><br>
</p>
<p>However, slab calculation and vacuum are computationally
expensive as you can read about in the following posts:</p>
<a class="moz-txt-link-freetext" href="https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg06138.html">https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg06138.html</a><br>
<a class="moz-txt-link-freetext" href="https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg09158.html">https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg09158.html</a><br>
<a class="moz-txt-link-freetext" href="https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg13625.html">https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg13625.html</a><br>
<p>So setting up such a calculation might be a waste of time if you
don't have access to computer hardware that is capable of doing
such a calculation.</p>
<p>A single personal desktop/laptop computer in my experience tends
to be insufficient when going beyond about simple unit cells and
small supercells with only a few atoms.</p>
<p>It may be that a group of GB networked computers is needed:</p>
<a class="moz-txt-link-freetext" href="https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg09334.html">https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg09334.html</a><br>
<a class="moz-txt-link-freetext" href="https://social.technet.microsoft.com/wiki/contents/articles/2539.diy-supercomputing-how-to-build-a-small-windows-hpc-cluster.aspx">https://social.technet.microsoft.com/wiki/contents/articles/2539.diy-supercomputing-how-to-build-a-small-windows-hpc-cluster.aspx</a><br>
<a class="moz-txt-link-freetext" href="https://diybigdata.net/personal-compute-cluster-2019-edition/">https://diybigdata.net/personal-compute-cluster-2019-edition/</a><br>
<a class="moz-txt-link-freetext" href="http://www.ssanalysis.co.uk/blog/spreading-the-load-an-abaqus-cluster-blog">http://www.ssanalysis.co.uk/blog/spreading-the-load-an-abaqus-cluster-blog</a>
<p>If that is not enough, a small rack or small high computing
cluster (HPC) may be needed:<br>
</p>
<a class="moz-txt-link-freetext" href="https://www.admin-magazine.com/HPC/Articles/real_world_hpc_setting_up_an_hpc_cluster">https://www.admin-magazine.com/HPC/Articles/real_world_hpc_setting_up_an_hpc_cluster</a><br>
<a class="moz-txt-link-freetext" href="http://techcenter.wikifoundrymobile.com/page/Dell+Life+Cycle+Controller+features+for+High+Performance+Computing+Cluster+Deployment">http://techcenter.wikifoundrymobile.com/page/Dell+Life+Cycle+Controller+features+for+High+Performance+Computing+Cluster+Deployment</a>
<p>It is also possible that may not be enough and a larger HPC may
be needed for such a calculation:</p>
<a class="moz-txt-link-freetext" href="https://uwm.edu/hpc/specifications-3/">https://uwm.edu/hpc/specifications-3/</a><br>
<a class="moz-txt-link-freetext" href="https://hpc.uni.lu/systems/gaia/">https://hpc.uni.lu/systems/gaia/</a><br>
<a class="moz-txt-link-freetext" href="https://www.isip.piconepress.com/projects/neuronix/html/neuronix_overview.shtml">https://www.isip.piconepress.com/projects/neuronix/html/neuronix_overview.shtml</a><br>
<a class="moz-txt-link-freetext" href="https://wiki.anunna.wur.nl/index.php/Architecture_of_the_HPC">https://wiki.anunna.wur.nl/index.php/Architecture_of_the_HPC</a><br>
<a class="moz-txt-link-freetext" href="https://www.delltechnologies.com/resources/en-us/asset/offering-overview-documents/ready-bundle-for-hpc-research-solution-overview.pdf">https://www.delltechnologies.com/resources/en-us/asset/offering-overview-documents/ready-bundle-for-hpc-research-solution-overview.pdf</a>
<p>It is of course difficult to generalize what would be needed
because computer hardware is very diverse as can be seen by
looking at the systems at the above links and the structures
(e.g., having different number of atoms) and calculation
parameters used vary computer resources for computation, such that
an attempt at running the calculation is sometimes the easiest why
to determine if it will compute or not [
<a class="moz-txt-link-freetext" href="https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg08136.html">https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg08136.html</a>
]. One example of a parameter you may already be familiar with
would be the number of k-points: <br>
</p>
<div><a
href="http://susi.theochem.tuwien.ac.at/reg_user/textbooks/WIEN2k_lecture-notes_2013/WIEN2k-getting_started.pdf"
target="_blank">http://susi.theochem.tuwien.<wbr>ac.at/reg_user/textbooks/<wbr>WIEN2k_lecture-notes_2013/<wbr>WIEN2k-getting_started.pdf</a>
(slide 10)</div>
<div><a
href="http://susi.theochem.tuwien.ac.at/reg_user/faq/kgen.html"
target="_blank">http://susi.theochem.tuwien.<wbr>ac.at/reg_user/faq/kgen.html</a></div>
<div><a class="moz-txt-link-freetext" href="https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg01053.html">https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg01053.html</a><br>
</div>
<div><br>
</div>
<div>Hopefully the above helps and good luck.<br>
</div>
<div><br>
</div>
<div class="moz-cite-prefix">On 11/9/2020 6:32 AM, Brik Hamida
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAETGc--cWx1fGOvoOw6sEEiMeeDtU4vLdpVTCV_tzUrAv-ZxCQ@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
Dear
<div><br>
</div>
<div>I am working on 2D structures and 2D heterostructures . I
want to know if the twisted angle can be done using Wien2k code.
If it is possible can someone explain how and thanks. </div>
<div><br>
</div>
<div>Best regards </div>
<div>Brik</div>
</blockquote>
<blockquote type="cite"
cite="mid:CAETGc--cWx1fGOvoOw6sEEiMeeDtU4vLdpVTCV_tzUrAv-ZxCQ@mail.gmail.com"></blockquote>
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