# [CP2K-user] COF cell optimize exploded

Linfeng Gan linfe... at gmail.com
Sun Apr 5 02:27:13 UTC 2020

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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.

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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