Assistance Required with fix MBX Command

[Ruye Li]

Dear MBX developers,

Thank you for your effort and time for developing MBX! I am currently working on integrating MBX water with a MOF system using LAMMPS, and I have encountered some difficulties with the fix MBX command. 

I have referred to the documentation available on GitHub. The documentation states the fix arguments are as follows:

```

 fix ID all mbx <number_of_monomer_types> <monomer_id_1> <lower_atom_type_index_of_mon1> <higher_atom_type_index_of_mon1> <number_of_atoms_of_mon1> <atom type of atom 1> <atom type of atom 2> ... <atom type of atom n1> <monomer_id_2> ... <monomer_id_N> ... json <name_of_json_file>

```

However, the examples provided in your repository don't seem to align with this syntax. For instance, the example command provided in lammps.in of mof_ff_lammps+6_h2o_mbx:

```

fix             1 all mbx 2 dp1 1 6 1 1 h2o 7 8 3 7 8 8 json mbx.json

```

I know dp1 should be the monomer that will not be passed on to MBX. But I'm very confused about what `dp1 1 6 1 1` represents, especially since dp1 is not explicitly defined in any other files.

For my specific case, where the MOF has 7 types of atoms, I try to configure the command as follows:

```

  fix 1 all mbx 2 dp1 1 7 1 1 H2O 8 9 3 8 9 9

```

But it results in an error message: "Unsupported molecule type in MBX (../fix_mbx.cpp:2489)." This suggests there might be an issue with how the monomers are defined in my LAMMPS input file, yet I am unable to find any definition or reference for dp1 in your documentation.

Could you please provide some guidance on how is dp1 defined and how can I correctly configure the monomer definitions for my MOF system to avoid errors? I would greatly appreciate any examples or additional documentation you could provide that would help clarify these issues.

Thank you for your assistance!

Best regards,

Ruye Li

[Philip Zhu]

Hi Ruye, please try lowercase "h2o".