[gmx-developers] Velocity update

[Jason de Joannis]

Quoting msuk2 at uiuc.edu:

> Dear gmx-developers,
>
> I was trying to simulate atoms moving with constant velocity. To do 
> that, to make it not affected by any force, i assigned huge mass 
> value so that F/m goes to zero. In that case, it does not simply give 
> same velocity value after one step. (The velocity became zero after 
> one step despite its huge mass value). So, it looks like some 
> correction is made if F/m goes to zero. I'd appreciate it very much 
> If you could answer me how velocity is updated in that case, and how 
> I can make it maintain its initial velocity. (Of course, I excluded 
> interaction between atoms)
>
> Thanks for your effort to develope GROMACS :-)
>
> All the best,
>
> Myungeun

How many particles do you have in your system? Are you sure that the 
center-of-mass adjustments aren't zeroing your velocity?

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\ Jason de Joannis  \
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