[gmx-users] Forces are large - How to track down the culprit

Mark Abraham Mark.Abraham at anu.edu.au
Tue Dec 30 01:59:00 CET 2008

Shay Amram wrote:
> Greetings dear Gromacs users,
> I have recently been simulating a POPG membrane* in water (SPC). Several 
> of my simulations after running well into the 10ns and 20ns are 
> sometimes getting a "Forces for atom X are large".  
> I'm rather unsure as to the cause of this situation. Moreover, as far as 
> I can tell from viewing the simulation, the system _does NOT_ explode 
> (as may be suggested by wiki.gromacs and some previous answers to this 
> kind of situation). The rest of the simulation looks much as it did in 
> the beginning.
> I would be interested (and thankful!) to hear any of your opinions as to 
> why I'm getting this message (or how to catch the culprit), and more 
> importantly, how to prevent it from happening in the future.

During this version-transitive period, it's always right to report the 
GROMACS version that you're using. It would normally be right to be 
using the most recent version (4.0.2) if encountering problems.


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