[gmx-developers] User defined constraint

[Ignacia Echeverria]

Hello,

I want to define costume constraint to be used in my MD simulations, i.e. constrain a group of atoms to move along a curved line.  I already did this in lammps but now I need to extend it to Gromacs. I'm not sure how plausible is to do this in gromacs and I would appreciate any suggestions of which would be the easiest way to implement this.

The basic steps are:

1) For a given group of atoms compute the center of mass.
2) Define the force acting over each of the atoms of the group which basically are of the form Fx = Fx(x,y,z), Fy = Fy(x,y,z) and Fz = Fz(x,y,z)
2) Add these extra forces to the forces that gromacs computes at every integration step.

I guess that I can make a custom function in pull.c? 

Thanks a lot for your help!

Best,

Ignacia Echeverria