Assigning atom id to atoms created by fix_deposit

Dear all lammpsers,

I am using fix deposit along with fix_evaporate for my system in which I create particles that move through a channel and are evaporated at the other end. I have a problem, because lammps automatically renames particles to particle 1 if there are no other particles present in the channel... I would like to know if I could change this such that all new created particles had a number associated with the sequential number of the particle as opposed to the number of the particle that exists in the system?

Thank you a lot in advanced.
With best wishes,

LAMMPS assigns a global ID to the deposited atom
that is one beyond any atom that currently exists in
the system. If you are saying that you continually
have 0 atoms in the system at the time
you deposit, then I’m not sure why you are running
MD on a single particle system most of the time.
I also don’t see why you care what the ID of
the particle is, since there is only 1 particle.
Can’t you post-process a dump file and figure
out which inserted particle it was?


Dear Steve, thanks for your quick reply! Apologies for not explaining everything properly. The problem is I am depositing 100 atoms at a certain rate; when some particles are evaporated, the new deposited particles get an atom ID that is not in the right sequence. So, after a while, my output becomes very messy, and because I don’t know how to control that, it is not easy to post process the files… I’d write a code to post process my data (which I do all the time), but in this case it looks rather difficult. Thank you again!

With best wishes,

I would try to think of a way to analyze what you want w/out relying
on atom IDs.


Added an “id max/next” option to the fix deposit command.

If you use id next, you should get the behavior you want,
where the IDs of deposited atoms increase one by one.

See if the default (id max) still works like the previous
version, and if id next now does what you want …


Dear Steve,

Thank you so very much! This fix does now work exactly in the way I wanted it to work! Thank you so much for all the effort that it took to help.

With best wishes,