[CP2K:7782] Re: R_CUTOFF vdWaals pair potential

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

Hi

In almost all parts of the program (exceptions are some DFTB and SE codes,
and maybe HFX) CP2K does not use the minimum image convention. It is save to use
interaction ranges that are larger than the simulation box.

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: Guilherme da Silva 
Sent by: cp... at googlegroups.com
Date: 05/23/2016 01:42PM
Cc: j.... at science.ru.nl
Subject: [CP2K:7782] Re: R_CUTOFF vdWaals pair potential

Hi,
I know that this one is a bit too old, but I have a similar doubt.

I think he argues about the possibility of high r_cutoff values to violate the minimum-image convention. Is that simply not true?

And if it does violate, have anyone some answer about what would be worse: to violate the mic or to not compute the dispersion correction in an appropriate range?

Regards,

Em terça-feira, 17 de dezembro de 2013 09:35:30 UTC-2, JanLos  escreveu:
  

    
  
  
    Dear CP2K developpers,

    I  was wondering about the comment in the section 

    "FORCE_EVAL/DFT/XC/VDW_POTENTIAL/PAIR_POTENTIAL/R_CUTOFF",

    saying "The cutoff will be 2 times this value". 

    If I stick to the default value of 10.06 Angstrom for this
    parameter, 

    the cut-off will be 20.12 Angstrom, which is pretty large, but OK. 

    If this is really what is applied, then it would imply that for a
    cubic simulation 

    box of 20 A cube with periodic boundary conditions, R_CUTOFF should
    not 

    be set larger than 5.0 Angstrom in order to NOT exceed recommended 

    maximal value for this box size, namely half the box size. Do I see
    this correctly ?

    It's just that the comment " The cutoff will be 2 times this
      value" confuses me, 

    asking myself why this input parameter been defined in this way.

    By the way, is the minimal image convention applied for the
    calculation

    of these interactions ?

                                                                  
    Regards,                  Jan Los

    

  





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