add warning to fix reaxff/species to explain the impact of large averaging

doc/src/fix_reaxff_species.rst

@@ -56,6 +56,17 @@ number of molecules of each species.  In this context, "species" means
 a unique molecule.  The chemical formula of each species is given in
 the first line.
 
+.. warning::
+
+   In order to compute averaged data, it is required that there are no
+   neighbor list rebuilds between the *Nfreq* steps. For that reason, fix
+   *reaxff/species* may change your neighbor list settings.  There will
+   be a warning message showing the new settings. Having an *Nfreq*
+   setting that is larger than what is required for correct computation
+   of the ReaxFF force field interactions can thus lead to incorrect
+   results.  For typical ReaxFF calculations a value of 100 is already
+   quite large.
+
 If the filename ends with ".gz", the output file is written in gzipped
 format.  A gzipped dump file will be about 3x smaller than the text version,
 but will also take longer to write.

src/REAXFF/fix_reaxff_species.cpp

@@ -115,7 +115,7 @@ FixReaxFFSpecies::FixReaxFFSpecies(LAMMPS *lmp, int narg, char **arg) :
     } else fp = fopen(arg[6],"w");
 
     if (!fp)
-      error->one(FLERR,"Cannot open fix reaxff/species file {}: {}",arg[6],utils::getsyserror()));
+      error->one(FLERR,"Cannot open fix reaxff/species file {}: {}",arg[6],utils::getsyserror());
   }
 
   x0 = nullptr;

src/RIGID/fix_rigid_small.cpp

@@ -2563,8 +2563,7 @@ void FixRigidSmall::write_restart_file(const char *file)
     auto outfile = std::string(file) + ".rigid";
     fp = fopen(outfile.c_str(),"w");
     if (fp == nullptr)
-      error->one(FLERR,"Cannot open fix rigid restart file {}: {}",
-                                   outfile,utils::getsyserror());
+      error->one(FLERR,"Cannot open fix rigid restart file {}: {}",outfile,utils::getsyserror());
 
     fmt::print(fp,"# fix rigid mass, COM, inertia tensor info for "
                "{} bodies on timestep {}\n\n",nbody,update->ntimestep);