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Hi Giovanni, <br>
<br>
thank you for your help. <br>
Actually I already tried to start the calculations with different
smearing values, or different mixing schemes. I also tried to add
small perturbations to the ionic positions, because I initially
thought that I was caught in the a "weird" state. But with no
improvements. <br>
I do not understand the issue, because if I start the calculations
with the atomic positions obtained after the first ionic relaxation
step, the scf calculation ran fine. It seems to me that if
'pot_extrapolation=none' and 'wfc_extrpolation =none', the scf
calculation at the n+1 ionic relaxation step does not use
information from the electronic structure relaxed at ionic step n
(i.e. it is equivalent to running a scf calculation from scratch).
Is somebody can confirm this aspect (or explain to me how and why I
am wrong?) ?<br>
<br>
Best regards<br>
<br>
Laurent<br>
<br>
<br>
<div class="moz-cite-prefix">On 19/12/2023 10:29, Giovanni Cantele
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAG=KO1F9SBKRq-qESNnsvgvGSXWJXvY8468ZbFMYmcELaexyUg@mail.gmail.com">
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<div dir="ltr" class="gmail_signature"
data-smartmail="gmail_signature">
<div dir="ltr"><span style="color:rgb(0,0,0)">Hi, I do not
have a precise explanation of that, but I can say that I
found such a behavior several times, in the years,</span></div>
<div><span style="color:rgb(0,0,0)">for completely different
systems. </span></div>
<div><span style="color:rgb(0,0,0)">And this concerns not
only the convergence of the scf step, but also the
relaxation</span></div>
<div><span style="color:rgb(0,0,0)">of the atomic
positions. </span></div>
<div><span style="color:rgb(0,0,0)">At some iteration it
seems that the algorithm falls in some "potential well"
and cannot exit it at all.</span></div>
<div><span style="color:rgb(0,0,0)"><br>
</span></div>
<div><span style="color:rgb(0,0,0)">In this respect, it
helps often just to restart the calculation from scratch
using one of the last coordinate sets found by</span></div>
<div><span style="color:rgb(0,0,0)">the pw.x, or in some
cases restart the code introducing in the coordinates
even very small perturbations (e.g. delete the</span></div>
<div><font color="#000000">digits from the fourth to the
last). In other cases, you might try to increase the
smearing, even just for a few steps, mostly if</font></div>
<div><font color="#000000">the problem is the convergence of
the scf cycle.</font></div>
<div><font color="#000000">This is just empirical, but it is
the signature for tricky calculations (where there is no
parameter</font></div>
<div><font color="#000000">to identify when a calculation is
going to become "tricky"!), where the presence of local
minima or other numerically hard problems, </font></div>
<div><font color="#000000">either with respect to the
charge density or with respect to the atomic positions,
can make the convergence non as easy as expected.</font></div>
<div><font color="#000000"><br>
</font></div>
<div><font color="#000000">Maybe, someone more expert might
add some more specific hints.</font></div>
<div><font color="#000000"><br>
</font></div>
<div><font color="#000000">Giovanni</font></div>
<div dir="ltr"><span style="color:rgb(0,0,0)"><br>
</span></div>
<div dir="ltr"><span style="color:rgb(0,0,0)">-- <br>
<br>
Giovanni Cantele, PhD<br>
CNR-SPIN<br>
c/o Dipartimento di Fisica<br>
Universita' di Napoli "Federico II"<br>
Complesso Universitario M. S. Angelo - Ed. 6<br>
Via Cintia, I-80126, Napoli, Italy<br>
<a href="mailto:giovanni.cantele@spin.cnr.it"
style="color:rgb(17,85,204)" target="_blank"
moz-do-not-send="true">e-mail:
giovanni.cantele@spin.cnr.it</a><br>
Phone: +39 081 676910<br>
Skype contact: giocan74<br>
<br>
ResearcherID: <a
href="http://www.researcherid.com/rid/A-1951-2009"
style="color:rgb(17,85,204)" target="_blank"
moz-do-not-send="true" class="moz-txt-link-freetext">http://www.researcherid.com/rid/A-1951-2009</a><br>
Web page: </span><a
href="https://sites.google.com/view/giovanni-cantele/home"
style="color:rgb(17,85,204)" target="_blank"
moz-do-not-send="true" class="moz-txt-link-freetext">https://sites.google.com/view/giovanni-cantele/home</a><br>
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<br>
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<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">Il giorno mar 19 dic 2023 alle
ore 08:49 Laurent Pizzagalli <<a
href="mailto:laurent.pizzagalli@univ-poitiers.fr"
moz-do-not-send="true" class="moz-txt-link-freetext">laurent.pizzagalli@univ-poitiers.fr</a>>
ha scritto:<br>
</div>
<blockquote class="gmail_quote"
style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Dear
all,<br>
<br>
I came across an issue I never encountered before. I performed
a simple <br>
ionic relaxation of a W cluster. The initial scf convergence
is <br>
achieved, the ionic forces are calculated (and are reasonable
for a <br>
first ionic relaxation step) and the new atomic positions are
obtained. <br>
The issue arises during the next scf calculation, which
diverges in a <br>
few steps. However, if I start a new calculation with the
updated ionic <br>
positions as input structure, the scf calculation runs
smoothly and <br>
converges (but the issue occurred again for the next ionic
relaxation <br>
steps).<br>
I obtained the same behavior with two different pw.x versions
(6.7 and <br>
7.1). I also tried to set 'pot_extrapolation = none', but with
no <br>
difference...<br>
<br>
Do any of you have an idea about the origin (and solution) of
this issue ?<br>
<br>
Thanks<br>
<br>
Laurent<br>
<br>
-- <br>
,,,
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<pre class="moz-quote-pre" wrap="">_______________________________________________
The Quantum ESPRESSO community stands by the Ukrainian
people and expresses its concerns about the devastating
effects that the Russian military offensive has on their
country and on the free and peaceful scientific, cultural,
and economic cooperation amongst peoples
_______________________________________________
Quantum ESPRESSO is supported by MaX (<a class="moz-txt-link-abbreviated" href="http://www.max-centre.eu">www.max-centre.eu</a>)
users mailing list <a class="moz-txt-link-abbreviated" href="mailto:users@lists.quantum-espresso.org">users@lists.quantum-espresso.org</a>
<a class="moz-txt-link-freetext" href="https://lists.quantum-espresso.org/mailman/listinfo/users">https://lists.quantum-espresso.org/mailman/listinfo/users</a></pre>
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<pre class="moz-signature" cols="72">--
,,, __,
/'^'\ |__|
( o o ) |
--------------------------------------------------oOOO--(_)--OO|o------
<a class="moz-txt-link-rfc2396E" href="mailto:Laurent.Pizzagalli@univ-poitiers.fr"><Laurent.Pizzagalli@univ-poitiers.fr></a>
<a class="moz-txt-link-freetext" href="http://laurent.pizzagalli.free.fr/">http://laurent.pizzagalli.free.fr/</a> Tel +33 549 49 74 99
------------------------------------------ Fax +33 549 49 66 92
Institut P'
Departement de Physique et de Mécanique des Matériaux
CNRS UPR 3346
Université de Poitiers
SP2MI
TSA 41123 .oooO
86073 Poitiers Cedex 9, FRANCE ( ) Oooo.
----------------------------------------------------\ (----( )-------
\_) ) /
(_/</pre>
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