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, for completely different systems. And this concerns not only the convergence of the scf step, but also the relaxation of the atomic positions. At some iteration it seems that the algorithm falls in some "potential well" and cannot exit it at all.
In this respect, it helps often just to restart the calculation from scratch using one of the last coordinate sets found by the pw.x, or in some cases restart the code introducing in the coordinates even very small perturbations (e.g. delete the 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 the problem is the convergence of the scf cycle. This is just empirical, but it is the signature for tricky calculations (where there is no parameter to identify when a calculation is going to become "tricky"!), where the presence of local minima or other numerically hard problems, either with respect to the charge density or with respect to the atomic positions, can make the convergence non as easy as expected. Maybe, someone more expert might add some more specific hints. Giovanni -- Giovanni Cantele, PhD CNR-SPIN c/o Dipartimento di Fisica Universita' di Napoli "Federico II" Complesso Universitario M. S. Angelo - Ed. 6 Via Cintia, I-80126, Napoli, Italy e-mail: [email protected] <[email protected]> Phone: +39 081 676910 Skype contact: giocan74 ResearcherID: http://www.researcherid.com/rid/A-1951-2009 Web page: https://sites.google.com/view/giovanni-cantele/home Il giorno mar 19 dic 2023 alle ore 08:49 Laurent Pizzagalli < [email protected]> ha scritto: > Dear all, > > I came across an issue I never encountered before. I performed a simple > ionic relaxation of a W cluster. The initial scf convergence is > achieved, the ionic forces are calculated (and are reasonable for a > first ionic relaxation step) and the new atomic positions are obtained. > The issue arises during the next scf calculation, which diverges in a > few steps. However, if I start a new calculation with the updated ionic > positions as input structure, the scf calculation runs smoothly and > converges (but the issue occurred again for the next ionic relaxation > steps). > I obtained the same behavior with two different pw.x versions (6.7 and > 7.1). I also tried to set 'pot_extrapolation = none', but with no > difference... > > Do any of you have an idea about the origin (and solution) of this issue ? > > Thanks > > Laurent > > -- > ,,, __, > /'^'\ |__| > ( o o ) | > --------------------------------------------------oOOO--(_)--OO|o------ > <[email protected]> > http://laurent.pizzagalli.free.fr/ 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. > ----------------------------------------------------\ (----( )------- > \_) ) / > (_/ > > _______________________________________________ > 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 (www.max-centre.eu) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users
_______________________________________________ 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 (www.max-centre.eu) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
