[gmx-users] The Warning: you should increase table-extension in your mdp file

[Justin A. Lemkul]

Chih-Ying Lin wrote:
> Hi
> I put a +1 charge molecule in gas phase and run MD without adding the
> Counter ions.
> And, I got the following warning:
> Although I checked the manual, I don't know how to increase the Table-extension.

It is an option in the .mdp file, however it is not recommended to adjust this 
parameter.  If you search your particular error message in the list archives, 
you will undoubtedly find that your system is blowing up, i.e.:

http://wiki.gromacs.org/index.php/blowing_up

You likely have something unphysical in your system that is causing extreme 
forces.  Investigate this further, because if atoms are flying apart, no 
increase of table-extension is likely to save them.

-Justin

> Thank you
> Lin
> 
> 
> 
> 
> Warning: 1-4 interaction between 12 and 19 at distance 1.469 which is
> larger than the 1-4 table size 1.000 nm
> These are ignored for the rest of the simulation
> This usually means your system is exploding,
> if not, you should increase table-extension in your mdp file
> 
> 
> table-extension: (1) [nm]
> Extension of the non-bonded potential lookup tables beyond the largest
> cut-off distance. The value should be large enough to account for
> charge group sizes and the diffusion between neighbor-list updates.
> This value also specifies the length of the lookup tables for the 1-4
> interactions, which are always tabulated irrespective of the use of
> tables for the non-bonded interactions.
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-- 
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Justin A. Lemkul
Graduate Research Assistant
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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