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Dear Giovanni,</div>
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Thanks a lot for your thorough explanation. I made the mistake to just look at the relative changes and they were rather large for a dual of 4 (with respect to 3). Anyways, thanks again for helping me to sort this out.</div>
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All the best,</div>
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Johannes</div>
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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 Giovanni Cantele <giovanni.cantele@spin.cnr.it><br>
<b>Sent:</b> Tuesday, March 1, 2022 7:03 PM<br>
<b>To:</b> Quantum ESPRESSO users Forum <users@lists.quantum-espresso.org><br>
<b>Subject:</b> Re: [QE-users] convergence testing very high dual parameter ecutrho for ultrasoft pseudopotential</font>
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<div class="" style="word-wrap:break-word; line-break:after-white-space">Dear Johannes,
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<div class="">I don’t know if I’ve well understood your point or if I’m missing something. However, after looking yo the plots you posted on Google Drive, it seems to me that actually your forces are fully converged even at the smallest values of ecutrho.</div>
<div class="">For example, in S.tif, I see the scale ranging from 0.130328 to 0.130340 Ry/a.u., about 1.e-5 wide. Similarly, just to consider another case, in O5.tif forces range from 0.45811 to 0.45815, about 4.e-5 wide (and if you discard the first point
the range is reduced by a further factor of 10).</div>
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<div class="">Now, the default value for convergence of forces is 1.e-3 a.u., see <a href="https://www.quantum-espresso.org/Doc/INPUT_PW.html#idm119" class="">https://www.quantum-espresso.org/Doc/INPUT_PW.html#idm119</a></div>
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<div class="">So, this means that your forces are much more converged than the threshold used by QE, unless you otherwise specified in your input.</div>
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<div class="">You can also see some sample convergence plots on forces here:</div>
<div class=""><a href="http://theossrv1.epfl.ch/Main/ElectronicTemperature" class="">http://theossrv1.epfl.ch/Main/ElectronicTemperature</a></div>
<div class="">The vertical axis spans a range of about 0.2 eV / A ~ 0.2 / 25.7 Ry / Bohr ~ 0.008 Ry / Bohr, again ~2-3 orders of magnitude larger that the same range in your plots.</div>
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<div class="">Giovanni</div>
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<div class="">On 1 Mar 2022, at 19:00, Johannes Meusburger - STFC UKRI via users <<a href="mailto:users@lists.quantum-espresso.org" class="">users@lists.quantum-espresso.org</a>> wrote:</div>
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<span lang="EN-US" class="">Dear all, </span></div>
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<span lang="EN-US" class="">I have observed a rather curious behaviour when performing convergence testing for CuSO4 x 5H2O. For the convergence testing I have displaced the oxygens surrounding the Cu and S atom by 10% of the equilibrium Cu-O and S-O bond lengths
and computed the forces on each of the atoms for various k-point grids, smearing widths (marzari-vanderbilt type), ecutrho and ecutwfc. To my surprise I found that the ecutrho value did not converge up to a dual parameter of 5 (i.e., wfc cut = 50 Ry and ecutrho
= 1000 Ry; forces vs dual parameter plots available on google drive:<a href="https://drive.google.com/drive/folders/1YaotezLaEHiSKouW19azGMdC6T8J-Jg8?usp=sharing" class="">https://drive.google.com/drive/folders/1YaotezLaEHiSKouW19azGMdC6T8J-Jg8?usp=sharing</a>). </span></div>
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<span lang="EN-US" class=""><span class=""> </span>I am using ultrasoft PP from the GBRV library, usually I find that a dual parameter of 2 or 3 (i.e., ecutrho 8 or 12 times larger than ecutwfc) yields well converged forces. My question now is if there is any
reason, why I should NOT use such a high dual parameter for the geometry optimization? </span></div>
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<span lang="EN-US" class="">All the best and many thanks, </span></div>
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<span lang="EN-US" class="">Johannes </span></div>
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<span lang="EN-US" class="">Johannes Meusburger<span class="x_Apple-converted-space"> </span> </span></div>
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<span lang="EN-US" class="">ISIS Neutron and Muon Source, UK </span></div>
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