Gcmc simulation warnings

Hi all,
I am using fix gcmc to simulate the water adsorption in the MOF by LAMMPS 2023. the simulation runs with warnings. These warnings include:

  1. WARNING: Communication cutoff 0 is shorter than a bond length based estimate of 7.002875. This may lead to errors. (src/comm.cpp:723)

  2. WARNING: Increasing communication cutoff to 15.112 for TIP4P pair style (src/KSPACE/pair_lj_cut_tip4p_long.cpp:484)

0 atoms in group FixGCMC:gcmc_exclusion_group:mygcmc
0 atoms in group FixGCMC:rotation_gas_atoms:mygcm

  1. WARNING: Neighbor exclusions used with KSpace solver may give inconsistent Coulombic energies (src/neighbor.cpp:654)

  2. WARNING: Bond/angle/dihedral extent > half of periodic box length (src/domain.cpp:936)

By proceeding the simulation, the following warning appear repeatedly (more than 100 times):

WARNING: Energy of old configuration in fix gcmc is > MAXENERGYTEST. (src/MC/fix_gcmc.cpp:793)

The trend of the number of adsorbed molecules is not correct. the number of adsorbed molecules increases in some steps and then fall to a small value and again goes up. I checked the mailing list and I think the problem arises from warnings 3 and 5. my simulation box is big enough and I used the input data file from the literature. Can anyone help me to find the problem?

These are all harmless. 1. and 2. are a side effect of using a TIP4P style, 3. and 4. a side effect of using fix gcmc with long-range Coulomb. In both cases the warnings are for the general case, but the specific implementation takes them into account.

This one warrants looking into. It could be caused by a bad topology and thus bonds stretching over a long distance. You should run a test simulation of the system without fix gcmc and check out the potential energies for bonds, angles, dihedrals and checkout a visualization of the trajectory to identify which bonded interactions may have problems.

Not 3. That is not a warning and completely harmless and expected.

Learning to understand and to resolve problems are an elementary step in learning how to do MD simulations correctly, and thus having others solve your problems for you is not a smart choice.

Thanks a lot for your valuable points. Just one thing, do you think the bellow warning could be the result of bad topology?
WARNING: Energy of old configuration in fix gcmc is > MAXENERGYTEST. (src/MC/fix_gcmc.cpp:793)

I have not seen this warning before, but I think you should first get your simulation to run cleanly without fix gcmc before looking into warnings issued by that fix. One step at a timeā€¦