[gmx-users] Forgotten velocities

Berk Hess gmx3 at hotmail.com
Fri Jul 1 14:00:06 CEST 2005

>From: Patrick Fuchs <Patrick.Fuchs at ebgm.jussieu.fr>
>Reply-To: Discussion list for GROMACS users <gmx-users at gromacs.org>
>To: gmx-users at gromacs.org
>Subject: [gmx-users] Forgotten velocities
>Date: Fri, 01 Jul 2005 13:03:50 +0200
>Dear gromacs users,
>I have started an md with gen_vel = no, starting from a system after 
>minimisation (thus by reading a gro file with the option -c in grompp). The 
>gro file after minimisation contains no velocities, but the system still 
>starts, and everything seems normal (I have checked temperature, the 
>different energies etc...). Can anybody tell me how the program generates 
>the velocities, and is there a default seed in such a case  (if yes, what's 
>its value) ?
>Thanks for your answer,

It does not generate velocities.
The forces are never binary exactly zero, so you get small velocities
which are scaled up by the temperature coupling.


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