This error message indicates that there's an issue with the order of commands in your LAMMPS input script. Let's break down the problem and provide a solution:

1. The error message states: "ERROR: Must define pair_style before Pair Coeffs (src/read_data.cpp:782)"
2. This means that in your input script or data file, you're trying to set pair coefficients before defining the pair style.

To resolve this issue, follow these steps:

1. Check your input script: Make sure you define the pair_style before reading the data file or setting any pair coefficients.
2. Correct order of commands: Your input script should generally follow this order: a. Units, dimension, boundary conditions b. Atom_style c. Pair_style d. Read_data command e. Pair_coeff commands (if not in the data file)

3. Example of correct order:

   units metal dimension 3 boundary p p p atom_style full pair_style lj/cut 10.0 # Or whatever pair style you're using read_data songchi-nvt-100ps-300-300 # Additional pair_coeff commands if needed # pair_coeff 1 1 0.2 2.5
4. Check your data file: If your pair coefficients are in the data file, make sure they're in the correct section and format.

5. Separate pair_style and read_data: Sometimes, it helps to separate these commands with a run 0 command:

   pair_style lj/cut 10.0 run 0 read_data songchi-nvt-100ps-300-300
6. Version compatibility: Ensure that your input script and data file are compatible with the version of LAMMPS you're using (29Aug2024-MSMPI in your case).
7. ASCII characters: The warning about non-ASCII characters suggests there might be some special characters in your input. Try to use only standard ASCII characters in your input files.

By following these steps, you should be able to resolve the "Must define pair_style before Pair Coeffs" error. If the problem persists, double-check both your input script and data file for any inconsistencies or errors.

This error message indicates that there's an issue with the order of commands in your LAMMPS input script. Specifically, it's trying to read pair coefficients before the pair style has been defined. Let's break down the problem and provide a solution:

1. Error explanation: "ERROR: Must define pair_style before Pair Coeffs" means that LAMMPS encountered pair coefficient information before a pair_style was specified.
2. Last command executed: "read_data songchi-nvt-100ps-300-300" suggests that the error occurred while reading your data file.

To resolve this issue, follow these steps:

1. Reorder your input script: Make sure you define the pair_style before reading the data file. Here's a general order to follow:

   units [your_units] dimension 3 boundary p p p atom_style [your_atom_style] pair_style [your_pair_style] read_data songchi-nvt-100ps-300-300 # Additional commands...
2. Check your data file: If your data file contains pair coefficients, make sure they're in the correct section and format.

3. Separate pair_style and read_data: Sometimes, it helps to separate these commands with a run 0 command:

   pair_style [your_pair_style] run 0 read_data songchi-nvt-100ps-300-300
4. Review your entire input script: Make sure all necessary styles (like atom_style, bond_style, etc.) are defined before reading the data file.
5. Version compatibility: Ensure that your input script and data file are compatible with your LAMMPS version.

By following these steps, you should be able to resolve the "Must define pair_style before Pair Coeffs" error. If you continue to have issues, you may want to share your complete input script (with any sensitive information removed) for further assistance.