[CP2K-user] [CP2K:17042] Re: Rhombohedral structure optimization (CELL_OPT)

[Matt Watkins]

Hello,
I think your structure / periodic boundaries are incorrect. When I run your 
input I see
"
 *** WARNING in particle_methods.F:684 :: The distance between the atoms 
 ***
 *** 78 and 89 is only 0.224 angstrom and thus smaller than the threshold 
***
 *** of 0.500 angstrom
"
this is going to lead to massive force and explosions.
Making your structure into a cubic conventional cell might make life easier.
Matt

On Thursday, 26 May 2022 at 02:49:51 UTC+1 Tomoki Ogata wrote:

> Hi there everyone,
>
> First time posting here, thank you in advance! 
> I am trying to do a structural optimization of FAU zeolite, which has a 
> rhombohedral unit cell (a = b = c = 17.9 A, alpha = beta = gamma = 60 
> degrees). 
>
> I tried running the input file attached, but unfortunately, the 
> crystallinity of the structure collapsed. 
>
> [image: structure_collapse.png]
>
> I believe that the reason is related to the line in my input file 
> "SYMMETRY RHOMBOHEDRAL", since the structure is preserved if this line is 
> excluded. However, without SYMMETRY RHOMBOHEDRAL, the a, b and c parameters 
> of the cell deviate from 17.9 A. I looked through the CP2K manual, but was 
> unfortunately unable to find any information which might help solve the 
> problem.
>
> A part of my input file which is attached:
> &CELL
>     &CELL_REF
>       A 12.6592017 12.6592017 0.0000000 
>       B 12.6592017 0.0000000 12.6592017 
>       C 0.0000000 12.6592017 12.6592017
>       MULTIPLE_UNIT_CELL 1 1 1
>       ALPHA_BETA_GAMMA 60 60 60
>       SYMMETRY RHOMBOHEDRAL
>     &END CELL_REF
>     A 12.6592017 12.6592017 0.0000000 
>     B 12.6592017 0.0000000 12.6592017 
>     C 0.0000000 12.6592017 12.6592017
>     MULTIPLE_UNIT_CELL 1 1 1
>     ALPHA_BETA_GAMMA 60 60 60
>     SYMMETRY RHOMBOHEDRAL
> &END CELL
>
> Would anyone happen to know of a way to do a structural optimisation for a 
> rhombohedral system while preserving the a, b and c parameters and without 
> the structure falling apart?
>
> Thank you in advance,
> Tomoki
>

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