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<div>If my memory serves me correctly “forc_conv_thr" does not correspond to the max forces on any atoms, I don’t remember exactly how it is calculated but it is a more complex expression. </div>
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By experience it is not always possible to reach very low forces on all atoms, especially if you are using some functional/corrections where the forces are not always perfectly consistent with the energy.
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<div>If you made sure that conv_thr is small enough so that non-scf correction to the forces is extremely small you might want to call pw.x as an energy/forces evaluator and interface it with a more specialised optimiser. Scipy(L)BFGS often does the trick for
me.
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<div>-----------------------------------------<br>
Tom Demeyere MSc<br>
PhD student<br>
Skylaris Research Group<br>
School of Chemistry, University of Southampton<br>
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<div>On 28 Dec 2023, at 16:39, Adam Michalchuk <a.a.l.michalchuk@bham.ac.uk> wrote:</div>
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<div>You don't often get email from<span class="Apple-converted-space"> </span><a href="mailto:a.a.l.michalchuk@bham.ac.uk">a.a.l.michalchuk@bham.ac.uk</a>.<span class="Apple-converted-space"> </span><a href="https://aka.ms/LearnAboutSenderIdentification">Learn
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Dear all, </div>
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I appreciate this topic has been discussed a number of times in the forum, with the answer that all components of all forces should satisfy the forc_conv_thr. This leads me to my probably very simple query that likely stems from a misunderstanding. </div>
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when I run a vc-relax calculation with e.g. a very tight forc_conv_thr=<span style="background-color: rgb(255, 255, 0);">1.0D-5</span>, my calculation finishes 'successfully' with e.g.:</div>
<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;"> </span></div>
<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;"> atom 1 type 3 force = 0.00000250 0.00000250 0.00000250</span></div>
<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;"> atom 2 type 3 force = 0.00000432 0.00000559 0.00000432</span></div>
<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;"> atom 3 type 3 force = 0.00000432 0.00000432 0.00000559</span></div>
<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;"> atom 4 type 3 force = 0.00000559 0.00000432 0.00000432</span></div>
<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;"> atom 5 type 2 force = -0.00000391 0.00000100 0.00000100</span></div>
<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;"> atom 6 type 2 force = 0.00000361 -</span><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt; background-color: rgb(255, 255, 0);">0.00001336
<span class="Apple-converted-space"> </span></span><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;">-0.00001336</span></div>
<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;"> atom 7 type 2 force = 0.00000100 -0.00000391 0.00000100</span></div>
<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;"> atom 8 type 2 force = 0.00000100 0.00000100 -0.00000391</span></div>
<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;"> atom 9 type 2 force = </span><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt; background-color: rgb(255, 255, 0);"> -0.00001336</span><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;">
-</span><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt; background-color: rgb(255, 255, 0);">0.00001336 </span><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;">0.00000361</span></div>
<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;"> atom 10 type 2 force = </span><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt; background-color: rgb(255, 255, 0);"> -0.00001336</span><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;">
0.00000361 -</span><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt; background-color: rgb(255, 255, 0);">0.00001336</span></div>
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<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;">even if I put rather ridiculous thresholds of forc_conv_thr=1.0D-7 it makes no real difference to the force
components:</span></div>
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<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;"> atom 1 type 3 force = -0.00000456 -0.00000456 -0.00000456</span></div>
<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;"> atom 2 type 3 force = 0.00000832 </span><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt; background-color: rgb(255, 255, 0);">0.00001867
</span><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;">0.00000832</span></div>
<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;"> atom 3 type 3 force = 0.00000832 0.00000832 0.00001867</span></div>
<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;"> atom 4 type 3 force = <span class="Apple-converted-space"> </span></span><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt; background-color: rgb(255, 255, 0);">0.00001867
</span><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;">0.00000832 0.00000832</span></div>
<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;"> atom 5 type 2 force = -0.00000414 -0.00000409 -0.00000409</span></div>
<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;"> atom 6 type 2 force = -0.00000040 -</span><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt; background-color: rgb(255, 255, 0);">0.00004042
<span class="Apple-converted-space"> </span></span><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;">-0.00004042</span></div>
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<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;">If I understand the output correctly, it appears as though some force components have converged fine, though
quite a few components have not reached the threshold, and changing the threshold makes little difference. As we do a lot of work on vibrational dynamics in dispersion bound crystals, tight forces are usually quite important. We've recently moved into using
QE and I'm trying to get to grips with how to control the forces in QE optimisations but am clearly missing something. Could anybody please point me in the right direction? </span></div>
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<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;">Many thanks in advance,</span></div>
<div style="direction: ltr;"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 11pt;">Adam</span></div>
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<span style="color: rgb(67, 67, 67);"> Adam Michalchuk </span></div>
<div style="margin: 0cm; font-family: Calibri, sans-serif; font-size: 11pt;"><span style="color: rgb(64, 64, 64);">University of Birmingham UK</span></div>
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