<div dir="ltr"><div><div><div><div><div><div><div><div>Dear Thomas,<br><br></div>thank you for your detailed reply!<br><br></div>If I understood this correctly, the ideal situation would be to have the slab in the center of the cell<br></div><div><br></div>Atom xx yy 0.5<br><br>(in crystal coordinates)<br><br></div><div>to center the dipole at 0% (=100% due to PBC) a reasonable choice would be emaxpos=0.95 and eopreg=0.10. In the dipole example they located the atoms around z=0 of the cells and put the dipole close to the center of the cell.<br><br></div><div>Muchas Gracias/Vielen Dank from Spain,<br><br></div><div>Christoph <br></div><div><br><br><br></div></div></div></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Apr 27, 2018 at 10:59 AM, Thomas Brumme <span dir="ltr"><<a href="mailto:thomas.brumme@uni-leipzig.de" target="_blank">thomas.brumme@uni-leipzig.de</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
Dear Chris,<br>
<br>
both planes of the dipole (the one at emaxpos and the one with the<br>
opposite charge at emaxpos+eopreg) have to be in the vacuum region.<br>
In fact, there should be enough space such that the wavefunctions
are<br>
essentially zero at the dipole planes. However, if the dipole is too
large,<br>
charge can spill into the vacuum region as plane waves are not
localized<br>
on the system and the charge could be in a lower energy state at the<br>
dipole. In other words. don't use 50 Angstrom of vacuum as this will
lead<br>
to a very low minimum in the total potential at the dipole.<br>
See also this paper:<br>
<br>
<a class="m_1612549424893121108moz-txt-link-freetext" href="https://journals.aps.org/prb/abstract/10.1103/PhysRevB.85.045121" target="_blank">https://journals.aps.org/prb/<wbr>abstract/10.1103/PhysRevB.85.<wbr>045121</a><br>
<br>
In this paper charged systems are discussed but similar things apply
to<br>
the dipole correction. Thus, if your system is centered at 50% of
the<br>
cell, center the dipole at zero and converge things with increasing
the<br>
size along z.<br>
<br>
Regards<br>
<br>
Thomas<div><div class="h5"><br>
<br>
<div class="m_1612549424893121108moz-cite-prefix">On 26.04.2018 14:00, Christoph Wolf
wrote:<br>
</div>
</div></div><blockquote type="cite"><div><div class="h5">
<div dir="ltr">
<div>
<div>
<div>
<div>
<div>
<div>
<div>Dear all,<br>
<br>
</div>
After trying for a few days I am still a bit puzzled
by the "proper application" of the dipole
correction. To test this I have made a sheet of
graphene added hydrogen below and fluorine above. I
then apply the following corrections:<br>
<br>
tefield = .true.<br>
dipfield =.true.<br>
<br>
</div>
and<br>
<br>
eamp = 0.00<br>
edir = 3<br>
emaxpos = 0.80 !(=16 Angstrom)<br>
eopreg = 0.10 ! (=2 Angstrom)<br>
<br>
</div>
The cell is 20 A in total. As I shift the layer from 0%
of the cell to 50% cell (whilst keeping above emaxpos at
80% and eopreg at 10% of the cell) the Fermi level
shifts slightly (~0.2-0.5 eV difference) and the
electrostatic potential (pp.x plot num 11 and then
planar average using average.x as in the work-function
example) is only "flat" in the vacuum region when the
sample is about 3A from the bottom of the cell (i.e. the
z coordinate of atoms has to be larger than 3 A).<br>
<br>
</div>
Reading the pw.x input I was under the impression that
only emaxpos has to fall into the vacuum but is there also
a "rule of thumb" for eopreg?<br>
<br>
</div>
Thanks in advance for your help!<br>
<br>
</div>
Best,<br>
</div>
Chris <br clear="all">
<div>
<div>
<div>
<div>
<div>
<div>
<div>
<div><br>
<br>
</div>
<div>PS: I saw the related discussion, but it does
not really answer this I think... <a href="http://qe-forge.org/pipermail/pw_forum/2009-December/089951.html" target="_blank">http://qe-forge.org/pipermail/<wbr>pw_forum/2009-December/089951.<wbr>html</a><br>
</div>
<div>-- <br>
<div class="m_1612549424893121108gmail_signature">
<div dir="ltr">Postdoctoral Researcher<br>
Center for Quantum Nanoscience, Institute
for Basic Science<br>
Ewha Womans University, Seoul, South Korea</div>
</div>
</div>
</div>
</div>
</div>
</div>
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</div>
<br>
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<br>
<pre class="m_1612549424893121108moz-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_1612549424893121108moz-txt-link-abbreviated" href="mailto:thomas.brumme@uni-leipzig.de" target="_blank">thomas.brumme@uni-leipzig.de</a>
</pre>
</font></span></div>
</blockquote></div><br><br clear="all"><br>-- <br><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr">Postdoctoral Researcher<br>Center for Quantum Nanoscience, Institute for Basic Science<br>Ewha Womans University, Seoul, South Korea<blockquote type="cite" style="font-size:12.8px"><div dir="ltr"><div><div dir="ltr"></div></div></div></blockquote></div></div>
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