[lammps-users] Representing an ion




Dear all,







I am trying to work on a MD simulation of ionic salt solutions. Some of the papers I came across have modeled the interactions considering ion-ion pair potentials. However, for a specific salt, sodium sulphate, interaction parameters between sodium ion and sulfate ion have been described. I am a little confused about the modeling of the sulfate ion. When considering such a potential model, the sulfate is treated as a single site (with all S-O) interactions being neglected. While the pair-potentials typically represent atom-atom interactions, modeling an interaction where one of the sites is an ionic radical is a little unclear to me. Any suggestions on how to model the sulfate as a single site using LAMMPS would be really helpful.







Thank you.



Ganesh

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Can you state the specfic interaction (e.g.a formula) that
you don't see how to do in LAMMPS?

Steve


Dear Steve and Lammps-users,


The issues I am trying to solve are—


1. Two interaction potentials are superimposed, namely, Sutherland potential (infinite repulsion for r<=sigma, and LJ attraction for r>sigma) and two-Yukawa potential. While I was able to modify the Yukawa potential in Lammps to apply the latter, any suggestions about the short range potential (Sutherland) would be helpful.

2. When modeling Na+ and sulfate ion interactions, in the pair coeff command should the i and j values correspond to that for Na and S ? All S-O interactions are neglected here. Should some other restriction be imposed on the sulfate so that Lammps knows that Na-S interaction is actually Na-sulfate interaction?


Thanks

Ganesh


— On Mon, 27/7/09, Steve Plimpton [email protected] wrote:


> From: Steve Plimpton <sjp[email protected]…33…24…>
> Subject: Re: [lammps-users] Representing an ion
> To: “Ganesh” <[email protected]…545…>
> Cc: “Lammps Users” <[email protected]…38…ists.sourceforge.net>
> Date: Monday, 27 July, 2009, 7:52 PM
>
> Can you state the specfic interaction (e.g.a formula) that
> you don’t see how to do in LAMMPS?
>
> Steve
>
> On Fri, Jul 24, 2009 at 10:46 AM, Ganesh<[email protected]…1418…> wrote:
> >
> > Dear all,
> >
> > I am trying to work on a MD simulation of ionic salt solutions. Some of the
> > papers I came across have modeled the interactions considering ion-ion pair
> > potentials. However, for a specific salt, sodium sulphate, interaction
> > parameters between sodium ion and sulfate ion have been described. I am a
> > little confused about the modeling of the sulfate ion. When considering such
> > a potential model, the sulfate is treated as a single site (with all S-O)
> > interactions being neglected. While the pair-potentials typically represent
> > atom-atom interactions, modeling an interaction where one of the sites is an
> > ionic radical is a little unclear to me. Any suggestions on how to model the
> > sulfate as a single site using LAMMPS would be really helpful.
> >
> > Thank you.
> >
> > Ganesh
> >
> > ________________________________
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> >
> > _______________________________________________
> > lammps-users mailing list
> > [email protected]
> > https://lists.sourceforge.net/lists/listinfo/lammps-users
> >
> >

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