<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body 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="moz-txt-link-freetext" href="https://journals.aps.org/prb/abstract/10.1103/PhysRevB.85.045121">https://journals.aps.org/prb/abstract/10.1103/PhysRevB.85.045121</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<br>
<br>
<div class="moz-cite-prefix">On 26.04.2018 14:00, Christoph Wolf
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAMC_G_4=J-sdVzcHJShk=840DfC6Z6tO8aeeK6GUDYaYMy+atA@mail.gmail.com">
<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"
moz-do-not-send="true">http://qe-forge.org/pipermail/pw_forum/2009-December/089951.html</a><br>
</div>
<div>-- <br>
<div class="gmail_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>
</div>
</div>
</div>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
users mailing list
<a class="moz-txt-link-abbreviated" href="mailto:users@lists.quantum-espresso.org">users@lists.quantum-espresso.org</a>
<a class="moz-txt-link-freetext" href="https://lists.quantum-espresso.org/mailman/listinfo/users">https://lists.quantum-espresso.org/mailman/listinfo/users</a></pre>
</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>
</pre>
</body>
</html>