[lammps-users] Unexpected Large displacement of atoms during equilibration

I am using LAMMPS for doing Cascade simulation. I am experiencing a strange error. During equlibration process at 100 K, I have seen that almost all the atoms are moving larger than the specified cut-off distance (0.3* lattice constant). From 21000 steps a few atoms moved by the specified distance and at ~30000 steps , almost all the atoms have moved. Note that, i have not introduced any high energetic particle at this stage.

The result is unreasonable. Can anybody plz mention where I am making the mistake? I am posting part of my INPUT file of relevance below.

Have you visualized the system and watched the atoms move?
Presumably they are doing something physical, else you will
see it.


Hi Steve,

It seems like your momentum is not conserved. Think about it. why it is happening?

At last I solved the problem. I made a silly mistake. In my simulation the system temperature is 100 K. But i did not initialize the atoms velocities and then rescaled the velocities to maintain the system temperature at 100 K. After incorporating the specific command “velocity…” , the simulation is giving expected results and without any shifting of the simulation box during equilibration phase.

Thanks for the help.

Vikas Varshney wrote: