[gmx-users] force

[Florian Dommert]

So I would assume you never wrote any forces in your trr file. The mdp
file option nstfout=0 is most probably set, isn't it ? If you use
-pforce you realize, that forces arise in your simulation, but you do
not tell gromacs to write them to a file. 

/Flo

* Shuangxing Dai <shuangxingdai at gmail.com> [2009-06-27 12:19:09 -0600]:

>Hi, all,
>    I was wondering about the force given by Gromacs. One is in the .trr  and .tpr file. When I read then with gmxdump, they are all zeros:
>
>traj.trr frame 0:
>   natoms=     24000  step=         0  time=0.0000000e+00  lambda=         0
>   box (3x3):
>      box[    0]={ 3.24900e+00,  0.00000e+00,  0.00000e+00}
>      box[    1]={ 0.00000e+00,  5.62743e+00,  0.00000e+00}
>      box[    2]={ 0.00000e+00,  0.00000e+00,  1.04120e+01}
>   f (24000x3):
>      f[    0]={ 0.00000e+00,  0.00000e+00,  0.00000e+00}
>      f[    1]={ 0.00000e+00,  0.00000e+00,  0.00000e+00}
>      f[    2]={ 0.00000e+00,  0.00000e+00,  0.00000e+00}
>      f[    3]={ 0.00000e+00,  0.00000e+00,  0.00000e+00}
>....
>
>When I use mdrun -pforce 0 to get all the non-zero force, I get:
>step 0  atom   4687  x    0.975    3.189    0.781  force  3.58158e+02
>step 0  atom   4688  x    0.975    3.189    0.586  force  7.16316e+00
>step 0  atom   4689  x    0.975    3.189    0.586  force  3.65324e+02
>step 0  atom   4690  x    0.812    3.095    1.041  force  3.58167e+02
>step 0  atom   4691  x    0.812    3.095    0.846  force  7.16314e+00
>....
>
>Why this happens? Thanks in advance.
>Shuangxing Dai
>_______________________________________________
>gmx-users mailing list    gmx-users at gromacs.org
>http://lists.gromacs.org/mailman/listinfo/gmx-users
>Please search the archive at http://www.gromacs.org/search before posting!
>Please don't post (un)subscribe requests to the list. Use the 
>www interface or send it to gmx-users-request at gromacs.org.
>Can't post? Read http://www.gromacs.org/mailing_lists/users.php

-- 
Florian Dommert
Dipl.-Phys.

Institute for Computational Physics
University Stuttgart

Pfaffenwaldring 27
70569 Stuttgart

Tel: +49 - 711 / 6856-3613
Fax: +49 - 711 / 6856-3658

EMail: dommert at icp.uni-stuttgart.de
Home: http://www.icp.uni-stuttgart.de/~icp/Florian_Dommert

!! PGP-ENCODED emails preferred !!
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 194 bytes
Desc: not available
URL: <http://maillist.sys.kth.se/pipermail/gromacs.org_gmx-users/attachments/20090627/bb96339c/attachment.sig>