How to set the initial velocity of the center of mass of a molecule?

LAMMPS LAMMPS General Discussion
1

Dear LAMMPS users and developers,

I would like to ask you if there is a command that allows to set the initial velocity of the center of mass of a molecule.

Currently, instead of directly fixing the initial velocity of the center of mass, I am fixing the initial velocity of each individual atom that constitues the molecule; which is equivalent from a mechanical point of view but I thought that it would much simpler if such a command exists.

Thank you,
Rafid.

2

No, such a command does not exist. What you describe is a very uncommon usage scenario. If you want more convenience, then I suggest you either use the python module
where you can extract and modify the velocity array directly (if done in serial) or use gather/scatter operations. Or you can write a tool that generates files for atomfile variables that then can be used in the velocity command.

3

Thank you !