AMBER Archive (2003)

Subject: Re: AMBER: NaCl ion pairs in TIP3P water box

From: M. L. Dodson (bdodson_at_scms.utmb.EDU)
Date: Wed Sep 24 2003 - 18:53:22 CDT

This seems like a problem that should be solvable by ab initio
methods, maybe?

Bud Dodson

Ioana Cozmuta writes:
>
> I did some simulations with KCl at 1M and SPC/M water for about 1ns. I've
> started with two different configurations: the first in which ions are
> randomly placed in the unit cell. The second in which I study crystal
> dissolution. I end up with approximately same average behaviour thus I
> think that at high concentration pairing and even clustering of ions is
> not impossible and that's what some experimental chemist think as well.
> It's a dynamic equilibrium however, not all the time the same ions
> pair/cluster.
>
> I also think that as long as we are unable to have a perfect model for
> water, we will not be able to model that accurately ionic solutions
> either. There are so many ff parameters for ions, some reproduce solvation
> energies better, some transport properties. So at best what can be done at
> the moment is to use the proper model for the purpose one wants to study.
>
> Just a short personal opinion...
>
> Ioana
>
> ****************************************************************************
> * Ioana Cozmuta, PhD * "Flatter me, and I may not believe you. *
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>
> On Wed, 24 Sep 2003, Bill Ross wrote:
>
> > Plus, the same-charge ion pairing occurs at 300K.
> >
> > Is there any evidence that ions don't pair in nature?
> >
> > Bill Ross
> >
  

-- 
M. L. Dodson                                bdodson_at_scms.utmb.edu
409-772-2178                                FAX: 409-772-1790

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