[CP2K-user] [CP2K:13056] COF cell optimize exploded

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

Hi

I assume your system is weakly bound in z-direction. Small force
changes in that direction can cause large changes.
The only obvious problem I could spot is the definition of the
reference cell. In order to minimize the effect of a change in 
volume, the reference cell should be larger than the initial
and final cell. I would set c=10 or 12 and I would also increase
the cutoff.
You could test this by just scan the energy as function of c and
correctly adapt the geometry of course.

regards

Juerg Hutter
--------------------------------------------------------------
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: "Linfeng Gan" 
Sent by: cp... at googlegroups.com
Date: 04/05/2020 04:27AM
Subject: [CP2K:13056] COF cell optimize exploded

   
  Hello all,
  I need some help about the covalent-organic frameworks (COF) 2D sheet cell optimize. After I optimized the COF with a 2X2X2 supercell, the cell size was totally exploded. I had kept the cell vectors and symmetry constant, changed different basis sets and different XC functions but the cell exploded anyway. 
  I had tried basis sets DZVP-MOLOPT-GTH and DZVP-MOLOPT-SR-GTH with PADE, PBE and BLYP. And the DFTD3 correction was also add to each calculation. The GAPW method I also had tried, but none of them worked. 
   
  Any suggestion is welcome, thanks!
  Linfeng
   
  The COF-5-2X2X2 supercell vectors should be:
  CELL_TOP| Volume [angstrom^3]:                                        21253.270
   CELL_TOP| Vector a [angstrom    60.040     0.000     0.000    |a| =      60.040
   CELL_TOP| Vector b [angstrom   -30.020    51.996     0.000    |b| =      60.040
   CELL_TOP| Vector c [angstrom     0.000     0.000     6.808    |c| =       6.808
   CELL_TOP| Angle (b,c), alpha [degree]:                                   90.000
   CELL_TOP| Angle (a,c), beta  [degree]:                                   90.000
   CELL_TOP| Angle (a,b), gamma [degree]:                                  120.000
   
  But after cell optimized calculation the output cell vectors are:
  *******************************************************************************
   ***                    GEOMETRY OPTIMIZATION COMPLETED                      ***
   *******************************************************************************
   
                      Reevaluating energy at the minimum
   
   CELL| Volume [angstrom^3]:                                            25653.623
   CELL| Vector a [angstrom]:      60.345     0.000     0.000    |a| =      60.345
   CELL| Vector b [angstrom]:     -30.173    52.260     0.000    |b| =      60.345
   CELL| Vector c [angstrom]:       0.000    -0.000     8.135    |c| =       8.135
   CELL| Angle (b,c), alpha [degree]:                                       90.000
   CELL| Angle (a,c), beta  [degree]:                                       90.000
   CELL| Angle (a,b), gamma [degree]:                                      120.000
    
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[attachment "COF-5-2X2X2.xyz" removed by Jürg Hutter/at/UZH]
[attachment "opt_cell.inp" removed by Jürg Hutter/at/UZH]