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Re: [lammps-users] [EXTERNAL] Re: slab correction in PPPM/disp and Ewald/disp
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Re: [lammps-users] [EXTERNAL] Re: slab correction in PPPM/disp and Ewald/disp


From: "reza N.Z" <mrn.nz91@...24...>
Date: Fri, 27 Oct 2017 11:22:56 +0330

Thank you Stan 

How can I benefit 2d Ewald in lammps? Should I use the slab-correction together with P P F boundary condition? 

Actually, I read your article " Liquid-vapor interface of Stockmayer fluid in a uniform external field (phys. rev. E 91, 022309(2015))". You were considered the long-range part of the Lenard-Jones interactions, the question is how did you implement it in the simulation? Did you apply a long cutoff radius like what Axel said? 


On Thu, Oct 26, 2017 at 7:56 PM, Moore, Stan <stamoor@...3...> wrote:
> So if I want to use PPPM/disp
> method I should cancel both coulombic and Lenard-Jones long-range
> interactions in z-direction while the slab-correction implemented in
> lammps just cancels the Coulombic one.

The Yeh Berkowitz slab correction in LAMMPS (for Coulombics) is only a first order correction anyway. Like Axel said, you'd be better off using a true 2D Ewald sum if you need that much accuracy. But it's probably overkill since your potential won't be that accurate either.

Stan

-----Original Message-----
From: Axel Kohlmeyer [mailto:akohlmey@...24...]
Sent: Thursday, October 26, 2017 7:56 AM
To: reza N.Z <mrn.nz91@...24...>
Cc: LAMMPS Users Mailing List <lammps-users@...396...sourceforge.net>
Subject: [EXTERNAL] Re: [lammps-users] slab correction in PPPM/disp and Ewald/disp

On Thu, Oct 26, 2017 at 4:47 AM, reza N.Z <mrn.nz91@...24...> wrote:
> I asked about non-neutral systems because I have not seen the
> sentence, which is added to the documentation, before and this
> questions comes to my mind that, might further changes is added to the slab correction.
> The system I want to perform is a slab-like system(neutral-system) in
> order to calculate surface tension. The impact of electric field is
> going to be studied on the system. As far as I know, it is essential
> to use slab-correction in z-direction. So if I want to use PPPM/disp
> method I should cancel both coulombic and Lenard-Jones long-range
> interactions in z-direction while the slab-correction implemented in
> lammps just cancels the Coulombic one.

now here is the $1,000,000 question:

how are you going to model the effect of the electric field at the same level of detail and accuracy?

axel.


--
Dr. Axel Kohlmeyer  akohlmey@...43...4...  http://goo.gl/1wk0 College of Science & Technology, Temple University, Philadelphia PA, USA International Centre for Theoretical Physics, Trieste. Italy.

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