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Dear Lorenzo and Giuseppe,</div>
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Thanks for the tips.</div>
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Indeed ecutfock = ecuwfc doesn't add significant error in energy convergence for my system (+0.1 meV/atom).<br>
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Then I changed the k-point grid from 3x2x3 to 2x1x2. 3x2x3 was perfectly converged for my system, and switching to 2x1x2 doesn't add significant error either (-0.1 meV/atom).<br>
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As a result, the scf calculation (keeping the same convergence parameters) with PBE0 is now only 5 times as long as PBE. With a very little trade-off, I think.</div>
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Thanks again!</div>
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Xavier<br>
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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 Giuseppe Mattioli <giuseppe.mattioli@ism.cnr.it><br>
<b>Sent:</b> Thursday, January 21, 2021 9:56 AM<br>
<b>To:</b> users@lists.quantum-espresso.org <users@lists.quantum-espresso.org><br>
<b>Subject:</b> Re: [QE-users] vc-relax with PBE0 and QE6.7</font>
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Dear Xavier<br>
Lorenzo is totally right, but there are two further parameters that <br>
can improve your experience with exact-exchange functionals in QE:<br>
<br>
1) ecutfock<br>
<br>
The cutoff for nonlocal integrals has a huge impact on computational <br>
resources. The default is ecutfock=ecutrho, but you rarely need that. <br>
In my experience, ecutfock=ecutwfc is quite satisfactorily for <br>
geometry optimizations, and ecutfock=1.5~2*ecutwfc is a sensible <br>
choice for properties calculation. You can test it on a small system.<br>
<br>
2) adaptive_thr=.true.<br>
<br>
In systems having no particular scf convergence issues, this generally <br>
provides a speedup of inner scf loops.<br>
<br>
HTH<br>
Giuseppe<br>
<br>
Quoting Lorenzo Paulatto <paulatz@gmail.com>:<br>
<br>
> Yes. It mostly depends on the choice of nq1x, nq2x and nq3x. <br>
> Local-density is linear in the number of k-points, but exact <br>
> exchange is quadratic, and it can get slow very quickly<br>
><br>
> Lorenzo Paulatto - Paris<br>
> On Jan 21 2021, at 4:14 pm, Bidault, Xavier <xavbdlt@uic.edu> wrote:<br>
>><br>
>> Thank you, Giuseppe. I tried with ONCV SG15 PP library and it went <br>
>> fine. However I wasn't expecting PBE0 to be so much longer than PBE <br>
>> for the same calculation. I don't have yet the whole convergence <br>
>> curve w.r.t. cutoff, but with the same convergence parameters, same <br>
>> k-point grid... PBE0 is 300-400x slower than PBE for an SCF <br>
>> calculation. Is it the right order of magnitude?<br>
>><br>
>> From: users <users-bounces@lists.quantum-espresso.org> on behalf of <br>
>> Giuseppe Mattioli <giuseppe.mattioli@ism.cnr.it><br>
>> Sent: Wednesday, January 20, 2021 6:22 AM<br>
>> To: users@lists.quantum-espresso.org <users@lists.quantum-espresso.org><br>
>> Subject: Re: [QE-users] vc-relax with PBE0 and QE6.7<br>
>><br>
>><br>
>><br>
>> Dear Xavier<br>
>> Forces can be calculated in the case of PBE0 and other hybrid EXX<br>
>> functionals if you use norm-conserving (NC) pseudopotentials. No,<br>
>> there is no way to perform calculations without pseudopotentials in QE.<br>
>> HTH<br>
>> Giuseppe<br>
>><br>
>> Quoting "Bidault, Xavier" <xavbdlt@uic.edu>:<br>
>> > Hello,<br>
>> ><br>
>> > I would like to run a geometry optimization (vc-relax) using PBE0<br>
>> > and QE6.7. I got the following error message:<br>
>> > Error in routine setup (1):<br>
>> > forces for hybrid functionals + US/PAW not implemented<br>
>> ><br>
>> ><br>
>> > I guess this means I have to rely on another software, don't I? Or<br>
>> > is there a way to discard the need of PP with PBE0 and QE6.7?<br>
>> ><br>
>> > Thank you,<br>
>> > Xavier<br>
>><br>
>><br>
>><br>
>> GIUSEPPE MATTIOLI<br>
>> CNR - ISTITUTO DI STRUTTURA DELLA MATERIA<br>
>> Via Salaria Km 29,300 - C.P. 10<br>
>> I-00015 - Monterotondo Scalo (RM)<br>
>> Mob (*preferred*) +39 373 7305625<br>
>> Tel + 39 06 90672342 - Fax +39 06 90672316<br>
>> E-mail: <giuseppe.mattioli@ism.cnr.it><br>
>><br>
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>> _______________________________________________<br>
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GIUSEPPE MATTIOLI<br>
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA<br>
Via Salaria Km 29,300 - C.P. 10<br>
I-00015 - Monterotondo Scalo (RM)<br>
Mob (*preferred*) +39 373 7305625<br>
Tel + 39 06 90672342 - Fax +39 06 90672316<br>
E-mail: <giuseppe.mattioli@ism.cnr.it><br>
<br>
_______________________________________________<br>
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