Smearing may alleviate convergence problems in any case where the latter are due to level crossing during the SCF cycle. Absolute energy errors are not necessarily a good metric of the accuracy of a pseudopotential calculation, as they depend sensitively on the details of the (pseudo) wave-function in the atomic core, which hardly affect the measurable chemico-physical properties of your system (such as e.g. forces and energy differences in general). SB
___ Stefano Baroni, Trieste -- http://stefano.baroni.me > On 23 Jun 2021, at 17:26, Bidault, Xavier <xavb...@uic.edu> wrote: > > > I would say that an energy cutoff of 25 Ry is way too small. I also work on > organic molecules, and I use 90 Ry (and 900 Ry for ecutrho) with PSlib 1.0.0 > US to get errors lower than 1 meV/atom. > > @Paolo: I wonder how relevant it is to use smearing in an organic compound > (unless it has conducting or semi-conducting capabilities). Could you tell > why it would be something to do? > > Xavier B. > From: users <users-boun...@lists.quantum-espresso.org> on behalf of Paolo > Giannozzi <p.gianno...@gmail.com> > Sent: Wednesday, June 23, 2021 2:04 AM > To: Quantum ESPRESSO users Forum <users@lists.quantum-espresso.org> > Subject: Re: [QE-users] scf of organic molecule does not converge > > It works decently well if you add a smearing (and a few more bands, but this > is done automatically): > occupations = 'smearing' > smearing = 'gaussian' > degauss = 0.01 > > Paolo > > On Wed, Jun 23, 2021 at 8:12 AM Haoran Wang <whr1...@gmail.com> wrote: > Hi QE users, > > I have been trying to run the scf of a molecule below for many days. It never > converged. The configuration is from Gaussian optimization, so it should be > sensible. I did try other configurations obtained from MD simulations and > still no convergence. I tried different pseudo-potentials (PBE-PAW, PBE-US, > LDA-US) and also tried tuning the parameters (mixing_beta, mixing_mode, > ecutrho...), still no convergence. Could somebody help me and see why this > happens? > > Thanks, > Haoran Wang > Utah State University > > ************************************************************************************** > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > users mailing list users@lists.quantum-espresso.org > https://lists.quantum-espresso.org/mailman/listinfo/users > > > -- > Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche, > Univ. Udine, via delle Scienze 206, 33100 Udine, Italy > Phone +39-0432-558216, fax +39-0432-558222 > > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > users mailing list users@lists.quantum-espresso.org > https://lists.quantum-espresso.org/mailman/listinfo/users
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