[CP2K-user] [CP2K:13186] Re: R_CUTOFF vdWaals pair potential

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

Hi

No, you need to specify the cutoff in the input file.

For periodic system you need to use an Ewald procedure for Coulomb.
The cutoff is only for the short range part, you can put the cutoff
for this part as large as you want, if you are ready to pay the
computer time. If it is a method which uses minimum image convention
the effective radius will be L/2 max.

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: "Austin clark" 
Sent by: cp... at googlegroups.com
Date: 04/27/2020 08:43PM
Subject: Re: [CP2K:13186] Re: R_CUTOFF vdWaals pair potential

Thanks Juerg,

I am running NPT simulations on molten salts. Is there a way to set the cutoff to always be 1/2 of the box length? Also what are the dangers of longer Coulombic cutoffs is in a system of monatomic ions?

On Wednesday, April 22, 2020 at 4:05:31 AM UTC-6, jgh wrote:Hi 
 
for long range Coulomb interactions in SE you should use the 
Ewald method. The Coulomb Cutoffs are then only for the  
short range atomic type dependent part. The short range part is  
minimum image. 
 
regards 
 
Juerg Hutter 
-------------------------------------------------------------- 
Juerg Hutter                         Phone : ++41 44 635 4491 
Institut für Chemie C                FAX   : ++41 44 635 6838 
Universität Zürich                   E-mail: h... at chem.uzh.ch 
Winterthurerstrasse 190 
CH-8057 Zürich, Switzerland 
--------------------------------------------------------------- 
 
-----c... at googlegroups.com wrote: ----- 
To: "cp2k" <c... at googlegroups.com> 
From: "Austin clark"  
Sent by: c... at googlegroups.com 
Date: 04/21/2020 06:33PM 
Subject: Re: [CP2K:13147] Re: R_CUTOFF vdWaals pair potential 
 
Hi all, 
 
I see that some SE codes do use the minimum image convention. Is the coulombic cutoff one of these, or can the cutoff be larger than one half of the cell length? 
 
Thanks,  
Austin 
 
 
 
On Monday, May 23, 2016 at 6:19:29 AM UTC-6, Guilherme da Silva wrote: 
Hi, 
 
Thanks for answering so fast! 
 
regards, 
 
Guilherme 
 
Em segunda-feira, 23 de maio de 2016 08:51:04 UTC-3, jgh  escreveu: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: h... at chem.uzh.ch  
Winterthurerstrasse 190  
CH-8057 Zürich, Switzerland  
---------------------------------------------------------------  
  
-----c... at googlegroups.com wrote: -----To: cp2k <c... at googlegroups.com>  
From: Guilherme da Silva   
Sent by: c... 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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