Trouble using the extForces parameters

From: Duster, Adam (
Date: Sat Apr 11 2015 - 04:11:42 CDT


I would like to call an external program to modify the gradients in NAMD. I have used the following parameters in the .conf file:

 run 1
 output withforces extout_namd

 extForces yes
 extCoordFilename pcs_coords
 extForceFilename 'forces'

Currently I am just trying to get this working with a small test system of 1 water molecule. I have written the following 'forces' file to test the program according to this page<> in the manual:

1 1 1 1 1
2 0 0 0 0
3 0 0 0 0

What I am trying to do is replace the x, y, and z forces in atom 1 with 1kcal/mol/A, and add 0 kcal/mol/A to the other atoms. However, I receive this error instead:

FATAL ERROR: Setting parameter extForces from script failed!

If anybody has any advice on how I can do this correctly I would be very grateful.

Thank you,

Adam Duster

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