[lammps-users] Equilibrating a spherical cluster of Silver atoms (FCC)


I am trying to equilibrate a spherical cluster of 141 Silver atoms (FCC) inside
a cubic box. I have used eam potential.

The code has run without any errors. But I observe from the 3D positions of the
atoms that the atoms move all over the spherical cluster approximately in
circles. I do not expect this. Other than the atoms at the surface, I expect
only oscillatory motion about mean positions for the atoms.

Is there a problem in my code (given below)? Any help would be much appreciated.


I think that the overall rotation of your system may come from a non zero angular momentum arising from the random initial velocities.
You can substract the angular momentum by adding the following line below the velocity command:
velocity all zero angular
Hope this helps,


Thanks a lot Vale and Wan Liang for your suggestions.

I modified the code first as suggested by Vale i.e. I added the "velocity all
zero angular" command. This time I found no circular motion (around the centre
of sphere) in xz or xy plane but in the yz plane.

Should I use the "fix momentum" command, as suggested by Wan Liang in addition
to this "velocity all zero angular" command? Or do I need not use the "velocity
all zero angular" command, if I am using "fix momentum" command?

I give the corrected portion of my code below.