[QE-users] DFT+U and surfaces -- convergence

[Christoph Wolf]

Hi Roberto,

a few things that might help

- different starting magnetization (if spin-polarized), e.g. a starting
magnetization of 0.4 could lead to a converged value of 0.7 but starting
from 0.7 might fail
- different surface-atom hubbard_U values: I played a bit with the linear
response formalism to determine Hubbard_U values and atoms on surfaces
seems to have a different response to hubbard_alpha
- dipfield (or related corrections using assume_isolated)
- sometimes it just takes very long electron_maxstep~300-500

if you have an input file I would be happy to try it a bit myself, these
"convergence problems" are very interesting to play with and overcome!

HTH!
Chris

On Sun, Jul 1, 2018 at 7:00 PM, <users-request at lists.quantum-espresso.org>
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>    1. DFT+U and surfaces -- convergence (Roberto Gomes de Aguiar Veiga)
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> Message: 1
> Date: Sat, 30 Jun 2018 11:28:07 -0300
> From: Roberto Gomes de Aguiar Veiga <roberto.veiga at ufabc.edu.br>
> To: users at lists.quantum-espresso.org
> Subject: [QE-users] DFT+U and surfaces -- convergence
> Message-ID: <f24f28cf195d18dc59ebdcd4ee64dbdf at ufabc.edu.br>
> Content-Type: text/plain; charset="us-ascii"
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>
>
> Dear Espresso users,
>
> my question is not related to any specific system, since it always
> happened to all of them. When I perform DFT+U calculations for bulk
> systems (e.g., NiO, Fe2O3, YIG, etc), they usually converge very
> quickly. However, when I try to perform calculations for the
> corresponding surfaces, they do not converge. I've been using
> mixing_mode='local-TF' and descreasing mixing_beta to values as low as
> 0.05 for the surface calculations, with no success. Can any of you with
> experience in this kind of simulation (DFT+U and surfaces) share what
> you usually do to have converged calculations?
>
> Best regards,
>
> Roberto
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-- 
Postdoctoral Researcher
Center for Quantum Nanoscience, Institute for Basic Science
Ewha Womans University, Seoul, South Korea
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