Dear all,

I am simulating a multi-component system for some reason. When I ask LAMMPS to read my first molecule file via:

read_data extra/atoms extra/bonds extra/impropers extra/improper/per/atom

The script works completely fine on my laptop having “LAMMPS-15Jun19” version. But when I use the same script on the cluster in which LAMMPS was built via “make mpi” command (I don’t exactly remember the version, probably it’s of 2016 or 2014), it throws an error “Illegal read command”. Is there any package missing in the LAMMPS version of the cluster or is there any other issue? Kindly help me to channel through this issue.

Thanking you in advance,

Deep M. Patel

Deal Deep,

as far as I know, the extra keywords are relatively new. You need to specify the same in the data file. Unfortunately, the LAMMPS website doesn't provide documentation for older versions, to my knowledge at least. However, you can use the Internet Archive (Wayback Machine) to check, if there were any changes.

Best wishes,

the LAMMPS manual is bundled with the LAMMPS (source) distribution. that is the version matching the code and should be used as a reference for that specific version of the code. one cannot expect that versions of a software that were release 3-5 years apart are fully compatible.
and we do recommend people to upgrade to recent versions of LAMMPS since the last 3-4 years have seen a concerted effort to significantly improve consistency and code quality of LAMMPS leading to many bugs being found and fixed. many of those were subtle and in hard to hit corner cases of the code, but still they are worth having and thus upgrading is worth the effort.


Dear all,

Thank you very much for the clarification.