[CP2K:10750] Problem in the preconditioner when using UKS

[hut... at chem.uzh.ch]

Hi

yes, these high spin state systems can be tricky to converge.
Your system did rather smoothly converge for me with the following
protocol:

- optimize with CG and OUTER_SCF every 10 steps until eps_scf 1.e-4.
- restart optimization with DIIS until eps_scf 1.e-7 (is rather slow at the end)

final energy:  -1170.0452882317 

regards

Juerg

--------------------------------------------------------------
Juerg Hutter                         Phone : ++41 44 635 4491
Institut für Chemie C                FAX   : ++41 44 635 6838
Universität Zürich                   E-mail: hut... at chem.uzh.ch
Winterthurerstrasse 190
CH-8057 Zürich, Switzerland
---------------------------------------------------------------

-----cp... at googlegroups.com wrote: -----
To: "cp2k" <cp... at googlegroups.com>
From: "Daniele Ongari" 
Sent by: cp... at googlegroups.com
Date: 09/19/2018 12:50PM
Subject: [CP2K:10750] Problem in the preconditioner when using UKS

Dear CP2K developers, 
I want to report a serious problem with the preconditioner when computing the energy of Fe-MOF-74 with UKS settings.
Long story short the energy goes down, it is close to convergence but then, after recomputing the preconditioner in the outer step it starts to diverge: see the image.






























Now, I attached the input and the output, but I already tried very different settings:
-smearing
-diagonalization without smearing
-different BS
-UKS false (converged, but to a higher energy, forcing the closed shell)
- starting magnetization on metals
- CG minimizer
- lower multiplicity
- 2x and 3x replicated unit cell in the shortest dimension
- lowering ENERGY_GAP to 0.001
These calculation ALL failed (I made 16 attempts in total, changing settings!).

And at the end the only one working (the 17th attempt, ironically the unlucky number for Italians!) was to use CG minimizer with no outer SCF, hence not recomputing the preconditioner. It converged after ~600 inner steps, to:

 HOMO - LUMO gap [eV] :    1.917671
 HOMO - LUMO gap [eV] :    0.235602

 ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):            -1170.045288008604075

Please let me know what was the problem, if it is a known issue of the preconditioner and how to circumvent it: for the moment I'm using no outer steps to have a robust convergence, but I know that this may cause the convergence to a local miniimum!

Thanks a lot!

Daniele 
PhD candidate, LSMO, EPFL Sion













  
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[attachment "energy.inp" removed by Jürg Hutter/at/UZH]
[attachment "energy.out" removed by Jürg Hutter/at/UZH]
[attachment "Fe-MOF-74_h111.subsys" removed by Jürg Hutter/at/UZH]