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Dear Yang,<br>
<br>
I have no clue how the Martyna-Tuckerman correction works but
usually one<br>
has problems with systems having such a large total charge since the
total<br>
cell needs to be neutral. Some terms are in fact calculated for a
charge neutral<br>
system resulting in a total potential which has a curvature as if
there would be<br>
a homogeneous background charge. This constant curvature leads to a<br>
potential energy minimum in the vacuum space between the repeated
cells.<br>
If you increase the cell this minimum goes down in energy and, at
some point,<br>
crosses the Fermi energy and gets occupied.<br>
<br>
Long story short:<br>
I have no clue but are you sure that Martyna-Tuckerman correction
works<br>
correctly for charged systems?<br>
Is the LUMO really a state of the molecule and not from a state in
the vacuum?<br>
<br>
You could check if everything works as intended for a neutral
system...<br>
<br>
Regards<br>
<br>
Thomas<br>
<br>
<br>
<div class="moz-cite-prefix">On 10/2/19 1:46 PM, Leo Yang wrote:<br>
</div>
<blockquote type="cite"
cite="mid:tencent_9AE1491B46369852087E7A69E6D083883108@qq.com">
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<p>Dear QE users:</p>
<p>I try to use QE-6.4.1 to simulate <img id="x_x_x__x0000_i1025"
style="width: 60.74pt; height: 18pt; cursor: pointer;"
src="cid:2609D217@08AB9A01.018E945D"
crossorigin="use-credentials" data-outlook-trace="F:3|T:3"
data-custom="AAMkADYyNGE5ZDVlLWI0M2ItNGNkYi04NWUzLTgwMDBiYmY4MWE1YgBGAAAAAADT1egYenlfTqNtjOrIuhcjBwBEgTiP%2FR2ETam0o5puADWEAAAAAAEJAABEgTiP%2FR2ETam0o5puADWEAALgunFEAAABEgAQAIdmOwWosi9FpfzF8EHcwG8%3D"
naturalheight="24" naturalwidth="81"
data-imagetype="AttachmentByCid"
originalsrc="cid:image002.png@01D55F54.3DEAB060"
moz-do-not-send="true"><font face="Calibri"> as single
molecule. The system is built in large super cell, and <em>total_charge=-4</em> is
added to input file leading to charged system. When I do the
convergence test in term of the super cell size (20 Angs - 30
Angs ), the variation for total energy is small: -1038.6784 Ry
for 20 Angs and 1038.7388 Ry for 30 Angs. But the band energy
and Fermi energy (5.23 ev to 3.08 ev) shift visibly. The
problem is that the band gap between band 104 (occupied) and
105 (unoccupied) become smaller with the increase of size
(about 0.81 ev change to 0.11 ev). It seems the band gap is
gradually disappear, which confuses me so much. The input file
is attached with this email. It will be very appreciated if
you can solve this for me. Thank you.</font></p>
<p><font face="Calibri"><br>
</font></p>
<p><font face="Calibri">Best wishes</font></p>
<p><font face="Calibri">Yang Zhou</font></p>
<p><font face="Calibri"><br>
</font></p>
<p><font face="Calibri">------</font></p>
<p><font face="Calibri">Yang Zhou</font></p>
<p><font face="Calibri">PhD student</font></p>
<p><font face="Calibri">University of Leeds</font></p>
<p><font face="Calibri">United Kingdom</font></p>
<br>
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<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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