[lammps-users] Question about com/chunk


I am using the LAMMPS (3 Mar 2020). I am trying to calibrate the bonded and non-bonded parameters of super atoms (cluster of explicit atoms) for coarse-graining, based on the center of mass of the super atoms (through Boltzmann inversion of bond parameters distribution). I have attached my equilibration input LAMMPS file and output Ovito file (for the output box dimensions). It is strange that the COM coordinates seem to be quite out of range of the simulation box at the end step. I have also attached the COM output file for your reference.

The output box dimensions are 43.3905A cube, whereas the difference between the min and max of the COM coordinates are -91.88773A, -85.4774A, and -90.2561A.
Also, in reference to one such issue in the discussion forum in 2015, I removed “ids once” from the com/chunk option.
Please let me know if you need further information. Thank you very much.

With best wishes,
Arunjyoti Sinha Roy.

COM_CG_output.txt (19.4 KB)

LAMMMPS_input.in (2.96 KB)

this is not strange at all. you are ignoring what is written in the “Note” in the documentation for compute com/chunk.