I have a system with about 46000 atoms. I also have about 62000 bonds between atoms. when I open the data file in OVITO or VMD or by read_data in LAMMPS, I got this error: “Unknown identifier in data file: 60134 1 43973 43974” but there are no mistakes in that line. when I put lines with indexes more than “60134” behind the “61034”, those lines read correctly so it seems I reach a maximum. it’s become weirder when I saw a similar problem in the other apps.
There may not be a problem in that specific line, but the error message happens because LAMMPS expected something else. This is usually an indication that the value for the number of atoms/bonds/angles/dihedrals/whatever is inconsistent with the actual number of entries.
The fact that this happens consistently with multiple independent implementations (Ovito, VMD) is further confirmation that your data file is incorrectly formatted.