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Hello again,</div>
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This is not really better with grid 3x2x3 (off-centered). See image below. Oscillations are visible on density, not much for pressure (but numbers end up periodic anyway). Pressure remains negative. However pressure oscillation decreases with higher number
of k-point (Gamma -> 2x1x2 off centered -> 3x2x3 off-centered), but there is still a large offset.</div>
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Note that SCF convergence of this organic crystal w.r.t. k-points is perfectly converged with 3x2x3 off-centered grid and PBE. Increasing the number of k-points for PBE0 may be better, but out of time for me. And my guess is it will not solve the pressure offset.</div>
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Concerning adding smearing, I don't see the point. This molecular system (known as not conductor) does not need it with PBE, so I don't know why I should add smearing with PBE0.<br>
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I gave a try to HSE instead of PBE0. Same oscillations. There is something wrong with vc-relax and hybrid xc functionals.<br>
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<img size="32180" contenttype="image/png" style="max-width: 100%; user-select: none;" unselectable="on" tabindex="-1" data-outlook-trace="F:1|T:1" src="cid:61a1742b-37e7-41bb-81af-c20dd2d531a6"></div>
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Best,</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> Bidault, Xavier <xavbdlt@uic.edu><br>
<b>Sent:</b> Tuesday, January 26, 2021 9:50 AM<br>
<b>To:</b> Quantum ESPRESSO users Forum <users@lists.quantum-espresso.org><br>
<b>Subject:</b> Re: [QE-users] vc-relax with PBE0 not converging</font>
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Hello,</div>
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My system is an organic molecular crystal (atoms C, H, N, O). The cutoff is chosen so there is 2 meV/atom error for SCF energy. The k-point grid 3x2x3 (off-centered) yields perfectly converged SCF energy. But to get faster with the vc-relax, I lowered it to
2x1x2 (off-centered), which introduces an error of only -0.1 meV/atom. I don't know if this is the reason why vc-relax density and pressure oscillate without converging.<br>
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I'm currently running v-relax with 3x2x3 grid... waiting for the result (10x slower)...</div>
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Thank you,</div>
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Xavier<br>
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<div id="x_divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> users <users-bounces@lists.quantum-espresso.org> on behalf of Paolo Giannozzi <p.giannozzi@gmail.com><br>
<b>Sent:</b> Monday, January 25, 2021 9:38 AM<br>
<b>To:</b> Quantum ESPRESSO users Forum <users@lists.quantum-espresso.org><br>
<b>Subject:</b> Re: [QE-users] vc-relax with PBE0 not converging</font>
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<div>Maybe the same problem reported here?</div>
<div> <a href="https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.com%2FQEF%2Fq-e%2F-%2Fissues%2F204&data=04%7C01%7Cxavbdlt%40uic.edu%7C3fdf0cc0f8bd4cd43e8308d8c14769ce%7Ce202cd477a564baa99e3e3b71a7c77dd%7C0%7C0%7C637471859758045446%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=QCUVoTzncfJfau7FM88IUZSHHmCHJf9wUl50miJJ4W4%3D&reserved=0" originalsrc="https://gitlab.com/QEF/q-e/-/issues/204" shash="bkX76AW8GvyWmULgV9fREiy0f0pQ0TaX2OH7CvftAGX11fdpeE/kr2d5RjGAU11+jFr5huZXwa6A+vfTOHB1Qz9MEBehhuSTIRsYiu6H1VnisoF4hP2NgrsvZd9CV8dZc8FEf0C8CeL2iu4wwGhTZgPvHm2M7uLBuvdMMvDeWDs=">
https://gitlab.com/QEF/q-e/-/issues/204</a></div>
<div>Paolo<br>
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<div dir="ltr" class="x_x_gmail_attr">On Mon, Jan 25, 2021 at 4:19 PM Bidault, Xavier <<a href="mailto:xavbdlt@uic.edu">xavbdlt@uic.edu</a>> wrote:<br>
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Hello,</div>
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I have a molecular crystal (1 unit cell = 56 atoms). I use SG15 ONCV 1.2 pseudopotential and Grimme D2 correction.<br>
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Using vc-relax with PBE, the structure converges, no problem.</div>
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But with PBE0, density and pressure oscillate without dampening (see figure below - Pressure remains negative, and not close to zero). Is there any particular strategy with PBE0?</div>
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<ul>
<li><span>vc-relax with PBE and then starting from the result and use PBE0?</span></li><li><span>relax with PBE0 and then vc-relax?</span></li><li><span>any simulation parameter to change (ion dynamics and/or cell dynamics - currently BFGS)?</span></li><li><span>any strategy with PBE0?</span></li></ul>
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<div>Thank you,</div>
<div>Xavier<br>
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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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