I encountered a discontinuity of energy when using ReaxFF. Namely, there is a rapid change of energy (few kcals/mol) when a bond in a diatomic molecule is being broken. The issue also occurs when an atom is being detached from a molecule. I checked the code and I believe that the change occurs, because the undercoordination term is not calculated when an atom does not have any bond. The simplest resolution I have found is removing if-statements from reaxc_multibody.cpp (lines 190, 205, 211) which restrict calculation of undercoordination term to bonded atoms.
Could someone confirm the presence of the issue?
I’m attaching a simple input script which shows the problem. I used the 31 May 2016 version of LAMMPS.
discontinuity_reaxFF.in (529 Bytes)