"pair_style reax/c" works but "pair_style reaxff" doesn't in lammps 29Oct20


I recently noticed that the reaxff pages have been updated on Lammps website.

The style name has been changed from “reax/c” to “reaxff”. Currently I only have lammps version 29Oct20 on our cluster and I tried to switch to “reaxff” in my simulation but an error occurred:

ERROR: Unrecognized pair style ‘reaxff’ (src/force.cpp:279)
Last command: pair_style reaxff lmp_control

Is it possible that the “pair_style reaxff” is not available in lammps 29Oct20 ?

And are there any underlying differences between the 2 pair_styles “reax/c” and “reaxff” ?

I appreciate any information that you provide ! Thanks a lot in advance !

If you use an older version of LAMMPS only the manual of that specific version applies to you.

If you want to learn about changes between LAMMPS versions, you have to read through the general release notes here: https://www.lammps.org/bug.html and https://www.lammps.org/bug2021.html, https://www.lammps.org/bug2020.html
or the more detailed release notes here: Releases · lammps/lammps · GitHub

The simplified explanation is that the LAMMPS developers are continually working on different parts of the code and sometimes we move things around or rename features.
This can have a variety of reasons. We try to do this in a backward compatible way, but - for obvious reasons - it is not possible to be forward compatible. In other words, when using an older version of LAMMPS, you have to be careful with the documentation, if that is for a more recent version of LAMMPS. You may see things that are not available or have been renamed or have changed semantics.

Thank you so much for the information !

I found the update that renamed “reax/c” to “reaxff” : Refactoring and improving REAXFF and QEQ packages by akohlmey · Pull Request #2708 · lammps/lammps · GitHub

In the future I will refer to the documentation of 29Oct20 before I upgrade to the latest version of lammps.