Are you weak or strong scaling? There is no ReaxFF support in the USER-INTEL package, so including that package won’t help. I’d recommend trying the USER-OMP package since a new threaded version of ReaxFF was merged into master GitHub today–you’ll need to make sure your version is updated though. You could also try the KOKKOS package, I’d recommend the MPI-only version for KNL. I’d also try using only 64 MPI per node instead of 68 MPI per node. Could also try using 128 MPI or 256 MPI per node if you aren’t using threading since each KNL core has 4 hardware threads.
Stan