<html><head></head><body><div class="yahoo-style-wrap" style="font-family:lucida console, sans-serif;font-size:13px;"><div dir="ltr" data-setdir="false">Of course, I fully agree with you !</div><div dir="ltr" data-setdir="false">Either you go with a 64 atoms cell (3.125 % doping) calculation which could take several weeks ... or just assume that the parameters obtained from 8 atoms unit cell (25% doping) are good enough and use them in the super cell.</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">For the U parameter, it could be safe to adopt the second strategy, since it is an on-site parameter. For the inter-site V, however, the local environment (the neighboring atoms) is important. <br></div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">A different method is hybrid functionals which are known to be accurate and can capture very well the missed physics.</div><div dir="ltr" data-setdir="false">You can for example try HSE 06. One can starts with pure ZnS to see the fraction of the EXX (HF exchange) needed to match the well known experimental results, and then use this fraction in the doped system.</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">This is just a suggestion... I can't say, but I guess that the calculation time would less than the few weeks of DFT+U+V.</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">Best <br></div><div dir="ltr" data-setdir="false">AH <br></div><div dir="ltr" data-setdir="false"> <br></div><div><br></div><div id="ydpd2bfb974yahoo_quoted_7181319018" class="ydpd2bfb974yahoo_quoted">
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On Wednesday, 22 May 2024 at 08:59:39 am GMT+1, Abdul Muhaymin <abdul.muhaymin@bilkent.edu.tr> wrote:
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<p>Dear Dr. HOUARI,<br clear="none">
<br clear="none">
Thank you for your reply. I did not correct the band gap in any
system. I am hoping if I apply some U parameter to Zn-3d, Co-3d
and maybe to S-3p, I can capture the physics better. In this
pursuit, some V parameter might also be an option. But this is not
the problem I am facing. I am facing problem on how to obtain
these U and V values. For undoped, periodic system, we can get the
value using hp.x with simple unit cell. But the problem is for
aperiodic doped system like the one I have. <br clear="none">
<br clear="none">
As you said, the calculated U from the 8 atoms ZnS unit cell is
probably okay to use for 64 atoms supercell. But if I dope the
unit cell (to get the U value of Co), this system (25% doping) is
much different than the 64 atoms supercell (3.125% doping). And
when I am trying to run hp.x directly for the 64 atoms (U applied
only to the single Co), only a single iteration of 1 q point takes
an hour using 2240 CPUs. So, it would take weeks to complete a
calculation! <br clear="none">
<br clear="none">
I am hoping maybe I can calculate the U parameter separately for
Co unit cell (i.e., Co-HCP) and then maybe for Zn and S from ZnS
unit cell. But I have no rationale to support that it should work.
And also the inter-site parameters cannot be obtained following
this. <br clear="none">
<br clear="none">
Sincerely,<br clear="none">
Abdul<br clear="none">
</p>
<div id="ydpd2bfb974yiv1636514288yqt50341" class="ydpd2bfb974yiv1636514288yqt5074942491"><div class="ydpd2bfb974yiv1636514288moz-cite-prefix">On 5/21/2024 7:03 PM, Abdesalem Houari
wrote:<br clear="none">
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<div dir="ltr"><font size="1">Dear Abdul
Muhaymen,</font></div>
<div dir="ltr"><font size="1"><br clear="none">
</font></div>
<div dir="ltr"><font size="1">You say that
your results are fine, except the band gap ! How did you
correct it in pure ZnS, before Co-doping ? <br clear="none">
</font></div>
<div dir="ltr"><font size="1">The most
commun way in DFT is hybrid functionals (like HSE 06),
which obviously are very demanding in computational cost.
So the DFT+U (+V) could be a nice alternative. Here I
think you might need on-site U not only for Co, but also
for Zn (and as you said may be S). Since ZnS is a band
insulator and covalent compound, the inter-site V could
play an important role.</font></div>
<div dir="ltr"><font size="1"><br clear="none">
</font></div>
<div dir="ltr"><font size="1">In principle
U and V <span><font style="background-color:inherit;" size="1">parameters are neither transferable nor
universal</font></span>, but in your case ( calculated
U from 8 atoms unit cell to use in 64 atoms supercell), I<span><font style="background-color:inherit;" size="1"> guess </font></span>it
should be OK !<br clear="none">
</font></div>
<div dir="ltr"><font size="1"><br clear="none">
</font></div>
<div dir="ltr"><font size="1">Best regards<br clear="none">
</font></div>
<div dir="ltr"><br clear="none">
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<div dir="ltr"> <br clear="none">
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<div dir="ltr" style="text-align:left;font-family:sans-serif;font-size:13px;"><font style="font-family:lucida console, sans-serif;" size="2">=============================</font><font size="2">========<br style="font-family:lucida console, sans-serif;" clear="none">
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<div><font size="2"><font style="font-family:lucida console, sans-serif;">Dr.
Abdesalem HOUARI</font></font></div>
<font size="2"><font style="font-family:lucida console, sans-serif;">-------------------------------------------------------------------------------------------</font><br style="font-family:lucida console, sans-serif;" clear="none">
<font style="font-family:lucida console, sans-serif;">Department
of physics, Theoretical Physics Laboratory</font><br style="font-family:lucida console, sans-serif;" clear="none">
<font style="font-family:lucida console, sans-serif;"><a shape="rect">University of Bejaia</a>-06000.
Algeria</font><font style="font-family:lucida console, sans-serif;">.</font><br style="font-family:lucida console, sans-serif;" clear="none">
<font style="font-family:lucida console, sans-serif;">E-mail: <span style="text-decoration-line:underline;text-decoration-style:solid;text-decoration-color:currentcolor;"><a shape="rect">abdeslam.houari@univ-bejaia.dz</a></span>
& <a shape="rect">habdslam@yahoo.fr</a></font><br style="font-family:lucida console, sans-serif;" clear="none">
<font style="font-family:lucida console, sans-serif;"><span style="text-decoration-line:underline;text-decoration-style:solid;text-decoration-color:currentcolor;background-color:rgb(0, 0, 255);font-style:italic;"></span></font><a shape="rect" style="font-family:lucida console, sans-serif;" href="https://sites.google.com/site/houariabdeslam/homepage" class="ydpd2bfb974yiv1636514288moz-txt-link-freetext" rel="nofollow" target="_blank">https://sites.google.com/site/houariabdeslam/homepage</a><br style="font-family:lucida console, sans-serif;" clear="none">
<font style="font-family:lucida console, sans-serif;">===================================</font><span style="font-family:lucida console, sans-serif;"></span></font><br clear="none">
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<div> On Tuesday, 21 May 2024 at 04:17:30 am GMT+1, Abdul
Muhaymin via users <a shape="rect" href="mailto:users@lists.quantum-espresso.org" class="ydpd2bfb974yiv1636514288moz-txt-link-rfc2396E" rel="nofollow" target="_blank"><users@lists.quantum-espresso.org></a>
wrote: </div>
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<div dir="ltr">Hello all,<br clear="none">
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<div dir="ltr"><br clear="none">
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<div dir="ltr">I am investigating single TM dopant in wide
band gap semiconductors such <br clear="none">
</div>
<div dir="ltr">as Co in ZnS. I am using a 64 atoms supercell
where I replaced one of <br clear="none">
</div>
<div dir="ltr">the Zn atom with a Co atom. I tested several
convergence with respect to <br clear="none">
</div>
<div dir="ltr">the supercell size. My results seem fine
except the band gap. Now I want <br clear="none">
</div>
<div dir="ltr">to apply the U correction to that Co-3d (and
maybe to S-2p). For this, <br clear="none">
</div>
<div dir="ltr">is it possible to use the unit cell (8 atoms)
and run hp.x to get the U <br clear="none">
</div>
<div dir="ltr">values? Or do I have to run hp.x with the
large supercell (2*2*2 unit <br clear="none">
</div>
<div dir="ltr">cell=64 atoms)?<br clear="none">
</div>
<div dir="ltr"><br clear="none">
</div>
<div dir="ltr">Also, at the beginning of our studies, during
the structural relaxation <br clear="none">
</div>
<div dir="ltr">phase, we first found our lattice parameter
for the host semiconductor <br clear="none">
</div>
<div dir="ltr">from multiple scf calculations and
subsequently running an eos analysis <br clear="none">
</div>
<div dir="ltr">(ev.x). Then we ran relax calculation but not
vc-relax. We keep this <br clear="none">
</div>
<div dir="ltr">lattice parameter constant and when
introducing new dopants, we only <br clear="none">
</div>
<div dir="ltr">vary the atomic positions
(calculation='relax'). In this case, when <br clear="none">
</div>
<div dir="ltr">running hp.x, could we replace the vc-relax
calculation with relax <br clear="none">
</div>
<div dir="ltr">calculation to self-consistently get the U
values?<br clear="none">
</div>
<div dir="ltr"><br clear="none">
</div>
<div dir="ltr">Thanks,<br clear="none">
</div>
<div dir="ltr">Abdul Muhaymin<br clear="none">
</div>
<div dir="ltr">Graduate (MS) student, Materials Science and
Nanotechnology<br clear="none">
</div>
<div dir="ltr">Bilkent University, Ankara.<br clear="none">
</div>
<div dir="ltr"><br clear="none">
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