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

[Austin clark]

Thanks again Juerg.

I'm using using CP2K 4.1, and there seems to be several references to EWALD 
in the manual. Do I need to enable all of them, or is there a specific one 
I am looking for?
Also, How can I tell if the method I am using uses minimum image or not? 
The log file is currently reporting the Coulombic cutoff as the specified 
value, and not half of the box size.

Thanks,
Austin

On Tuesday, April 28, 2020 at 4:55:54 AM UTC-6, jgh wrote:
>
> 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: h... at chem.uzh.ch 
> <javascript:> 
> Winterthurerstrasse 190 
> CH-8057 Zürich, Switzerland 
> --------------------------------------------------------------- 
>
> -----c... at googlegroups.com <javascript:> wrote: ----- 
> To: "cp2k" <c... at googlegroups.com <javascript:>> 
> From: "Austin clark" 
> Sent by: c... at googlegroups.com <javascript:> 
> 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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