[QE-users] Convergence issue in relaxation calculation

[Omar A. Ashour]

 Be careful translating VASP input files directly into QE because the
implementation details can differ, so just converting the units isn’t
enough.

electron_maxtep = 3000 —> if you can’t converge in a couple hundred steps,
you should really take a step back and assess what your system is doing.
Your calculation did 628 steps, and the SCF accuracy was all over the
place--the last step is ~2 Ry. Something is clearly wrong.

Increasing your cutoff to at least 60 Ry will possibly fix your convergence
problems. VASP’s PAW sets are incredibly soft; you can’t just convert their
cutoff to Ry and expect it to work with a different pseudopotential. Read
the UPF files for your pseudos: Ga has a suggested cutoff of 60 Ry, and
that’s the minimum you should use.

Other notes:

   1. Your pseudos are wrong. QE implements SOC differently than VASP. You
   need to use fully relativistic pseudos.
   2. If this is metallic, use cold smearing with a larger degauss; your
   k-grid is somewhat coarse. It will probably help convergence, too.
   3. conv_thr is very large; there is no good reason to go above the
   default 1e-6 for a cell of this size, and you may need to go lower
   depending on what you’re trying to do. Note that QE’s implementation is
   different from VASP’s, see equation A7 in this paper, and I believe it’s
   missing a factor of V^2/2 with V the cell volume.
   4. for_conv_thr is far too large; again, don’t go above the default
   unless you have a good reason. If I recall correctly, QE applies the force
   convergence criteria to each component, whereas VASP applies it to the
   magnitude of the force, which is something to be aware of.
   5. It won’t make a difference here for this system, but if you use
   ibrav=0 you should have more decimal places in your CELL_PARAMETERS card
   (10 or so) or the symmetry analysis may not work properly.


You’re relaxing a noncolinear magnet, so due to the complicated energy
landscape, you should expect more difficult convergence, even with a proper
input file.

Best,

Omar A. Ashour
UC Berkeley

On Sep 7, 2024 at 1:53:16 AM, Bhargab Kakati <bhrgabkakati at iasst.res.in>
wrote:

> On 2024-09-05 23:58, Bhargab Kakati wrote:
>
> Thank you so for your suggestion, I'll try and get back yo you if I
>
> encounter some issues.
>
>
> Regards,
>
> Bhargab
>
>
> On 5 Sept 2024 5:13 pm, sogenyi at student.eaifr.org wrote:
>
>
> > Dear Kakati,
>
> >
>
> > I think you need to apply same condition for ecut and ecutrho when
>
> >
>
> > using ultrasoft potential to PAW pseudopotential i.e ecutrho = 8 or
>
> > 10
>
> > times ecut.
>
> >
>
> > Sunday.
>
> >
>
> > Quoting Bhargab Kakati <bhrgabkakati at iasst.res.in>:
>
> >
>
> >> Dear experts,
>
> >>
>
> >> I am trying to relax my alloy system but it is not converging even
>
> >
>
> >> after running for a very long time. I hava attached here the input
>
> >
>
> >> and outputs of the run. Any help in resloving the issue would be
>
> >
>
> >> highly appreciated.
>
> >>
>
> >> Regards,
>
> >> Bhargab Kakati
>
> >
>
> > _______________________________________________
>
> > 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 users at lists.quantum-espresso.org
>
> > https://lists.quantum-espresso.org/mailman/listinfo/users
>
> Thank you so for your suggestion, I'll try and get back yo you if I
>
> encounter some issues.
>
>
> Regards,
>
> Bhargab
>
>
>
> On 5 Sept 2024 5:13 pm, sogenyi at student.eaifr.org wrote:
>
> >
>
> > Dear Kakati,
>
> >
>
> > I think you need to apply same condition for ecut and ecutrho when
>
> > using ultrasoft potential to PAW pseudopotential i.e ecutrho = 8 or
>
> > 10
>
> > times ecut.
>
> >
>
> > Sunday.
>
> >
>
> >
>
> > Quoting Bhargab Kakati <bhrgabkakati at iasst.res.in>:
>
> >
>
> > > Dear experts,
>
> > >
>
> > > I am trying to relax my alloy system but it is not converging even
>
> > > after running for a very long time. I hava attached here the input
>
> > > and outputs of the run. Any help in resloving the issue would be
>
> > > highly appreciated.
>
> > >
>
> > > Regards,
>
> > > Bhargab Kakati
>
> >
>
> >
>
> > _______________________________________________
>
> > 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 users at lists.quantum-espresso.org
>
> > https://lists.quantum-espresso.org/mailman/listinfo/users
>
>
> Hello,
>
> I tried to relax my system bu increasing ecutrho = 8 times of ecut and
> also changed the pseudopotentials too. It is still not converging. I
> have attached the new input and output files here.
>
> Regards,
> Bhargab
> _______________________________________________
> 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 users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users
>
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