Invalid LAMMPS data file

Hi, all
I am trying to generate LAMMPS data of 9 repeating melamine-formaldehyde using charmm2lammps.pl. I use LAMMPS 29Oct20 to run the input file.

The parameters of CHARMM FF are extracted from https://www.swissparam.ch/ which are used subsequently to generate *.psf file. The generated parameter file resulted in several impropers with all improper coefficients 0 (zero). But the generated LAMMPS data showed 0 impropers.

The problem is that I can’t run the LAMMPS input file due to the invalid data file section of improper. Anyone could help me please how to solve this. For consideration, I save the files in LAMMPS - Google Drive

Thanks.

Regards,
Tony

You can just delete the “improper types” and “impropers” lines from the data file header and similarly the “Impropers” and “Improper Coeffs” sections. Since your system has no impropers, it is not a problem. I would presume the charmm2lammps.pl script is making certain assumptions that were trigered by the force field files you have provided that are not met by your specific system.

Hello, Axel
Thank you for your suggestions. It is working now.

Regards,
Tony