[CP2K-user] [CP2K:16474] Re: Prevent Cell Geometry/Vectors From Changing

[fabia...@gmail.com]

Hi Lenard,

in cp2k there are two types of optimizations, GEO_OPT and CELL_OPT. In 
GEO_OPT the lattice vectors are fixed and only the atomic positions are 
optimized. In a CELL_OPT both the lattice vactors and the atomic positions 
can be relaxed simultaneously.

So if you don't want the box to change you need 
RUN_TYPE GEO_OPT 
and  the
&MOTION
  &GEO_OPT
  &END
&END
section.

If the SCF does not converge the forces (and pressure) are probably very 
bad and thus the optimizer (e.g. BFGS) takes unreasonable steps. If the SCF 
does not converge you should probably stop the simulation and improve SCF 
stability.

Cheers,
Fabian
On Thursday, 20 January 2022 at 05:50:59 UTC+1 lenardc... at gmail.com wrote:

> Hi there. So, I've been doing a few geometry optimizations and I have seen 
> that for some of them, the cell vectors change, sometimes a bit other times 
> a lot. This especially happens when the SCF run is not converged multiple 
> times in a row. The thing is, I don't want the cell vectors to change, I 
> don't want the atoms to go outside of the box, yet it still happens. Can 
> you give me any tips/ideas on how to do a geometry optimizations where 
> atomic positions can only change and the cell geometry cannot, or is this 
> not feasible?
>
> Kind regards,
> Lenard
>

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