[gmx-users] K+ atom type and KCl crystals

[Erik Lindahl]

Hi,

Just for reference, the K+ parameters now used in OPLS-AA (both my 
Gromacs version and Bill Jorgensen's own files) are the ones derived by 
Johan Åqvist and not the original OPLS ones.

It was a couple of years ago that I last looked into it, but they are 
quite good (better than any alternatives available then) and 
parameterized to reproduce the experimental free energy of solvation in 
water.

Cheers,

Erik

On Jan 27, 2005, at 11:55 AM, Marc Baaden wrote:

>
> Hi,
>
> We had the same issue about K+ parameters. Currently we do use
> the OPLSAA K+ with the Gromos forcefield. Find attached the included
> file. But be aware that mixing forcefields is an insecure domain
> (although ions are always an issue).
>
> BTW, concerning K+ and in particular KCl, we have witnessed a number
> of crystallization events of KCl crystals at physiological 
> concentration
> with Amber, but not with Gromacs so far.
>
> Have other people also seen this ? I guess it's a K+ parameter problem.
> Any tips or tricks ?
>
> Cheers,
>   Marc Baaden
>
>
> <k+oplsaa.itp> Dr. Marc Baaden  - Institut de Biologie 
> Physico-Chimique, Paris
>  mailto:baaden at smplinux.de      -      http://www.marc-baaden.de
>  FAX: +33 15841 5026  -  Tel: +33 15841 5176  ou  +33 609 843217
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