<div dir="ltr">Thank you all for your answers and explanation. Adding smearing does make things work now. <div><br></div><div>Thanks,</div><div>Haoran</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Jun 23, 2021 at 12:45 PM Stefano Baroni <<a href="mailto:baroni@sissa.it">baroni@sissa.it</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="auto">Smearing may alleviate convergence problems in any case where the latter are due to level crossing during the SCF cycle. Absolute energy errors are not necessarily a good metric of the accuracy of a pseudopotential calculation, as they depend sensitively on the details of the (pseudo) wave-function in the atomic core, which hardly affect the measurable chemico-physical properties of your system (such as e.g. forces and energy differences in general). SB<br><br><div dir="ltr"><div><span style="background-color:rgba(255,255,255,0)">___</span></div><div><span style="background-color:rgba(255,255,255,0)">Stefano Baroni, Trieste -- <a href="http://stefano.baroni.me" target="_blank">http://stefano.baroni.me</a></span></div></div><div dir="ltr"><br><blockquote type="cite">On 23 Jun 2021, at 17:26, Bidault, Xavier <<a href="mailto:xavbdlt@uic.edu" target="_blank">xavbdlt@uic.edu</a>> wrote:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr">
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I would say that an energy cutoff of 25 Ry is way too small. I also work on organic molecules, and I use 90 Ry (and 900 Ry for ecutrho) with PSlib 1.0.0 US to get errors lower than 1 meV/atom.</div>
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@Paolo: I wonder how relevant it is to use smearing in an organic compound (unless it has conducting or semi-conducting capabilities). Could you tell why it would be something to do?</div>
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Xavier B.<br>
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<div id="gmail-m_-5407093619571607621divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> users <<a href="mailto:users-bounces@lists.quantum-espresso.org" target="_blank">users-bounces@lists.quantum-espresso.org</a>> on behalf of Paolo Giannozzi <<a href="mailto:p.giannozzi@gmail.com" target="_blank">p.giannozzi@gmail.com</a>><br>
<b>Sent:</b> Wednesday, June 23, 2021 2:04 AM<br>
<b>To:</b> Quantum ESPRESSO users Forum <<a href="mailto:users@lists.quantum-espresso.org" target="_blank">users@lists.quantum-espresso.org</a>><br>
<b>Subject:</b> Re: [QE-users] scf of organic molecule does not converge</font>
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<div>It works decently well if you add a smearing (and a few more bands, but this is done automatically):<br>
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<div> occupations = 'smearing'</div>
smearing = 'gaussian'<br>
<div> degauss = 0.01</div>
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<div>Paolo<br>
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<div dir="ltr">On Wed, Jun 23, 2021 at 8:12 AM Haoran Wang <<a href="mailto:whr1130@gmail.com" target="_blank">whr1130@gmail.com</a>> wrote:<br>
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<div dir="ltr">Hi QE users,
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<div>I have been trying to run the scf of a molecule below for many days. It never converged. The configuration is from Gaussian optimization, so it should be sensible. I did try other configurations obtained from MD simulations and still no convergence. I
tried different pseudo-potentials (PBE-PAW, PBE-US, LDA-US) and also tried tuning the parameters (mixing_beta, mixing_mode, <span style="color:rgb(0,0,0);font-family:monospace;font-size:medium">ecutrho...</span>), still no convergence. Could somebody help
me and see why this happens?</div>
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<div>Thanks,</div>
<div>Haoran Wang</div>
<div>Utah State University</div>
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<div>Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,<br>
Univ. Udine, via delle Scienze 206, 33100 Udine, Italy<br>
Phone +39-0432-558216, fax +39-0432-558222<br>
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