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<p>Dear Asad,</p>
<p>please also answer to the list ;) ("reply all")<br>
</p>
<p>No! It's either dipfield = .true. or assume_isolated ='2d'. If
you want to simulate "a real" 2D system using<br>
the Coulomb cutoff you don't need to correct due to the systems
dipole. And if you correct with the artificial<br>
dipole, cutting of the Coulomb will result in something
bad/weird... Actually, I don't know if this will work at all.<br>
<br>
So, either dipfield = .true. or assume_isolated ='2d'</p>
<p>Thomas<br>
</p>
<br>
<div class="moz-cite-prefix">On 11/13/18 11:45, Asad Mahmood wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAPKVScxjWYJZba5JuEK_1=KNySc3QFEKD=Fexb2_0rioHEk8BQ@mail.gmail.com">
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<div dir="auto">Thanks Thomas for reply. So I need to include both
flags(i.e dipfielf = .true and assume_isolated ='2d' ) in relax
or structure optimization calcations ?</div>
<br>
<div class="gmail_quote">
<div dir="ltr">On Tue, Nov 13, 2018, 3:11 PM Thomas Brumme <<a
href="mailto:thomas.brumme@uni-leipzig.de"
moz-do-not-send="true">thomas.brumme@uni-leipzig.de</a>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF"> Dear Asad,<br>
<br>
What is the benefit of using dipfield=.true.? Well, the
benefit is that you get the correct electronic structure,<br>
energetics, and so on. As you want to simulate a 2D system
with 3D boundary conditions this is the only<br>
correct way if you have an asymmetric system (in the
z-direction, assuming the 2D system is in xy). Well,<br>
not the only correct way. Recently a Coulomb cutoff
technique was implemented in QE, check input flag<br>
assume_isolated='2D'<br>
<br>
Regards<br>
<br>
Thomas<br>
<br>
P.S.: If you have a dipole in your system you'll see that
properties (especially the total energy) will change<br>
with increasing vacuum region. If you increase it, you'll
minimize the eigenfunction overlap between the<br>
repeated layers but the Coulomb interaction will never be
zero and thus you can get wrong results - and<br>
this will be worse for larger dipole, e.g., the flourinated
graphene.<br>
<br>
<div class="m_1700344142664914731moz-cite-prefix">On
11/13/18 08:38, Asad Mahmood wrote:<br>
</div>
<blockquote type="cite">
<div dir="auto">Hi,
<div dir="auto"><br>
</div>
<div dir="auto">I have a hexagonal graphene(or any
other) monolayer and I hydrogenate(or flourinate,
etc.) on the top surface only (single sided). Is there
need to use flag dipfield = .true ? What is benefit or
disadvantage of using this flag for optimization of
L.C or bond length?</div>
<div dir="auto">I am using 20 angstrom vacuum between
two layers to avoid mutual influence.</div>
</div>
<br>
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<br>
<pre class="m_1700344142664914731moz-signature" cols="72">--
Dr. rer. nat. Thomas Brumme
Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry
Leipzig University
Phillipp-Rosenthal-Strasse 31
04103 Leipzig
Tel: +49 (0)341 97 36456
email: <a class="m_1700344142664914731moz-txt-link-abbreviated" href="mailto:thomas.brumme@uni-leipzig.de" target="_blank" rel="noreferrer" moz-do-not-send="true">thomas.brumme@uni-leipzig.de</a>
</pre>
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</blockquote>
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</blockquote>
<br>
<pre class="moz-signature" cols="72">--
Dr. rer. nat. Thomas Brumme
Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry
Leipzig University
Phillipp-Rosenthal-Strasse 31
04103 Leipzig
Tel: +49 (0)341 97 36456
email: <a class="moz-txt-link-abbreviated" href="mailto:thomas.brumme@uni-leipzig.de">thomas.brumme@uni-leipzig.de</a>
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