[gmx-users] Problems for checking the equilibrium of Ionic liquid system

[Florian Dommert]

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On 10/28/2010 06:22 AM, hui sun wrote:
> Dear GMX users,
>  
> Now, I am doing some simulations about ionic liquids. The
> problem I am encountering  is how to check the equilibrium of Ionic
> liquid system. The boss asks me to do the RSMD to check it, but I think
> it is not right. Could you give me some useful advice?
>  
> Thank you very much for your attentions!
>  
>  
> With best wishes!
>  
> Hui Sun
>  

Hello,

 be careful when simulation ionic liquids. I do not know what kind of
force field you use, but I assume the one of Lopes and Padua. This force
field has problems in reproducing correct dynamics, in other words the
diffusion is too slow. We tested this and also other force fields, but
dynamics seems to be always the problem. Static properties are
represented quite well, however it takes a look time to get into
equilibrium. We performed simulations of 100ns and started the analysis
after 20ns, if I remember correctly. A possiblity to check if the system
is in equilibrium would be to calculate the diffusion in x,y, and z
direction seperately and when all plots show normal diffusion,
equilibrium should be reached. For further information check my
homepage, where you can find some references for papers dealing with
this topic.

/Flo



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- -- 
Florian Dommert
Dipl.-Phys.

Institute for Computational Physics

University Stuttgart

Pfaffenwaldring 27
70569 Stuttgart

Phone: +49(0)711/685-6-3613
Fax:   +49-(0)711/685-6-3658

EMail: dommert at icp.uni-stuttgart.de
Home: http://www.icp.uni-stuttgart.de/~icp/Florian_Dommert
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