[gmx-users] editing velocities in tprs

Alex Robertson alexrson at stanford.edu
Wed Jul 6 18:08:17 CEST 2005

how do you grompp velocities?  Would I put have to extract them into a gro 
and then grompp that?

I don't think that which time step I take the velocities from matters 
because it's only a femtosecond difference and I'm not trying to test 

Alex Robertson
----- Original Message ----- 
From: "Berk Hess" <gmx3 at hotmail.com>
To: <gmx-users at gromacs.org>
Sent: Wednesday, July 06, 2005 12:54 AM
Subject: RE: [gmx-users] editing velocities in tprs

>>From: "Alex Robertson" <alexrson at stanford.edu>
>>Reply-To: Discussion list for GROMACS users <gmx-users at gromacs.org>
>>To: "Discussion list for GROMACS users" <gmx-users at gromacs.org>
>>Subject: [gmx-users] editing velocities in tprs
>>Date: Tue, 5 Jul 2005 15:00:46 -0700
>>    I am trying to take some tprs that I have created and create new one's 
>> with all the velocities inverted.  Does anyone know how to edit the 
>> information in tprs?  Or how to take the output from gmsdump and turn 
>> that into a run input file?
> I guess the easiest thing is editing grompp to reverse the velocities.
> But why do you want to do this?
> If it is for reversibility test of the leap-frog integrator
> you also have to take the velocities of the next step,
> as the velocitities are stored at half steps.
> Berk.
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