how to implement the custom dump styles for atoms displacment, and atom group-ID

Dear LAMMPS developers,

I have been using LAMMPS for a while along with commercial DEM codes. LAMMPS does provide some really cool features that the later one does not have.

However, I am facing some issues to output/visualize the results:

  1. Atoms displacement

Suppose there is a Variable named AtomDisp (accumulated displacement)

set the AtomDisp[i] = 0 at the beginning of simulation (i is atom ID), and then do:

for (i = 0, i<= N, i++) // N: total number of atoms

// displacement of atom i during n --> n+1 step
tmpDisp = sqrt( (x[i]n - x[i](n-1))^2 + (y[i]n - y[i](n-1))^2 +(z[i]n - z[i](n-1))^2 );
AtomDisp[i] = AtomDisp[i] + tmpDisp; // accumulated displacement


so is there easy way to implement such atom attribute, and use it like:

dump dmpID … vx vy vz AtomDisp …

  1. dump atoms group-ID
    so that we can clear observe the movement of atoms between different groups.

This is a good feature in commercial codes, but in LAMMPS i could not manage to do this. Until now I just set the same radii or density to the atoms in specific groups, in order that the atoms have same colour in same group.

So how to add this feature just like atom type or other properties for dump command?
dump dmpID … vx vy vz group-ID …


David Long

There is a compute displace/atom, which calculates the
quantity above. You can dump it with each

atom in a custom dump file. See Section 6.15 of

the manual for info on how to dump all kinds of
quantities, from computes, fixes, variables.