[CP2K-user] [CP2K:11269] Cell optimization of layered material, convergence vs K_POINTS

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

Hi

the LBFGS is a totally different optimizer code using the LBFGS
method for the Hessian update. It should be preferred also because
of the reduced memory usage for large systems.

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: 02/14/2019 06:03PM
Subject: Re: [CP2K:11269] Cell optimization of layered material, convergence vs K_POINTS

Dear prof. Hutter,
thanks for your advice.

 I tried and:
1) EPS_DEFAULT E-12 and E-14 did not fix the problem
2) &CELL_REF (https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/QMMM/CELL/CELL_REF.html) did not work: I'm not sure if I chose the settings correctly, being a non orthogonal cell. However, what is this command supposed to do? I could not find a proper reference to read more.
This is what  I used:
   &SUBSYS 
      &CELL 
         A  30.1669436651   0.0             0.0            
         B  -15.0834720617  26.1253399655   0.0            
         C  -5.88681146004e-16 1.15003884889e-16 8.07826742778  
         &CELL_REF
            A   35.0   0.0  0.0
            B  -20.0  30.0  0.0
            C    0.0   0.0 10.0
         &END CELL_REF
      &END CELL

3) LBFGS did work but now I'm a little confused/worried, how is the "low memory" version of  BFGS supposed to be more stable? Is it always a good choice for my crystals, e.g, with a number of atoms that goes from 50 to >1000?

Finally, if it is a problem with the optimizer, why did it work with kpoints or doubling the UC?

Here is the plot of my results:

Thank you very much for your help!

Daniele














  
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