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<p>Dear Antoine,</p>
<p><br>
</p>
<p></p>
<div>> As the resulting U are drastically different (>1eV),<br>
> what is the criterium that we should use to decide wich is the "good" projector for a given system?</div>
<p></p>
<p><br>
</p>
<p>In Quantum ESPRESSO, two types of projectors are supported for DFT+Hubbard: "atomic" and "ortho-atomic". In other codes there are other projector types. So, for Quantum ESPRESSO, at present we can choose only between "atomic" and "ortho-atomic". Which one
is better? From our experience, "ortho-atomic" seems to be better, but we are performing more extensive comparisons. It may also depend on the property you are interested in. Therefore, I would suggest to investigate both types of projectors (with they respective
U (and V) values) for your system and see whether the results are similar or there are significant differences. But if you cannot do so, I would start with "ortho-atomic". As written here
<a href="http://theossrv1.epfl.ch/Main/DFTHubbard" class="OWAAutoLink" id="LPlnk373351" previewremoved="true">
http://theossrv1.epfl.ch/Main/DFTHubbard</a> :</p>
<p>"<i><span>Ortho-atomic orbitals seem to provide more accurate results - maybe because if atomic (i.e. non-orthogonal) orbitals are used, the Hubbard correction can be added twice in the regions where orbitals overlap, or, when using the U alone, the orthogonalisation
procedure makes the system more "aware" of the presence of the ligands (but, at the end, we think the most general approach is to use both U and V in a ortho-atomic formulation).</span></i>"<br>
</p>
<p><br>
</p>
<p>HTH</p>
<p><br>
</p>
<p>Cheers,</p>
<p>Iurii<br>
</p>
<p><br>
</p>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> users <users-bounces@lists.quantum-espresso.org> on behalf of Antoine Jay <ajay@laas.fr><br>
<b>Sent:</b> Wednesday, August 26, 2020 11:52:43 AM<br>
<b>To:</b> Quantum ESPRESSO users Forum<br>
<b>Subject:</b> Re: [QE-users] ?==?utf-8?q? U calculation, different projection type</font>
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<div>Dear Iurii,<br>
As the resulting U are drastically different (>1eV),<br>
what is the criterium that we should use to decide wich is the "good" projector for a given system?<br>
<br>
Regards,<br>
<br>
Antoine Jay<br>
LAAS-CNRS<br>
Toulouse, France<br>
<br>
Le Mercredi, Août 26, 2020 11:13 CEST, Timrov Iurii <iurii.timrov@epfl.ch> a écrit:<br>
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<p>Dear Sergey,</p>
<p> </p>
<p>As Lorenzo said, yes this is expected. Ab initio U depends on the Hubbard manifold, i.e. which projector functions are used (e.g. atomic, orthogonalized atomic, Wannier functions, you name it). So it is absolutely important to report in papers which projector
functions were used for the calculation of U. In particular, this is why one should be very careful when comparing U values from different papers. There are also other factors that influence the value of U (pseudopotentials, oxidation state, functional, one-shot
or self-consistent calculation). We have some papers in preparation on this topic, which hopefully would clarify a bit more these points. You can also check this web page:
<a class="x_OWAAutoLink" id="LPlnk684825" href="http://theossrv1.epfl.ch/Main/DFTHubbard">
http://theossrv1.epfl.ch/Main/DFTHubbard</a></p>
<p> </p>
<p>Greetings,</p>
<p>Iurii</p>
<p> </p>
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<font size="3" face="'Times New Roman', Times, serif" color="808080">--<br>
Dr. Iurii TIMROV<br>
Postdoctoral Researcher</font></div>
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<div id="x_divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri, sans-serif" color="#000000"><b>From:</b> users <users-bounces@lists.quantum-espresso.org> on behalf of Lorenzo Paulatto <paulatz@gmail.com><br>
<b>Sent:</b> Wednesday, August 26, 2020 10:59:13 AM<br>
<b>To:</b> users@lists.quantum-espresso.org<br>
<b>Subject:</b> Re: [QE-users] U calculation, different projection type</font>
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<div class="PlainText"><font size="2"><span style="font-size:10pt;">> Is it expected behavior?<br>
<br>
Yes,<br>
kind regards<br>
<br>
> Thanks,<br>
> Sergey<br>
<br>
--<br>
Lorenzo Paulatto - Paris<br>
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