[lammps-users] ATC

I am trying the ATC code form example folder which was present in lammps folder. I am facing an issue during the calculation of J -integral. Even I am a new user for atc package, how to proceed if any suggestion will be a great help for me.
This is the error I am getting
ERROR: Could not find fix_modify ID (…/modify.cpp:933)
Last command: fix_modify PK1 mesh create 10 10 1 SYSTEM p f p

There is not enough information here to give specific advice.
The only file with that exact command line in the LAMMPS distribution runs fine, so I would presume the error is due to some modification you made to the input.
The error message itself is self explanatory and can be understood from the fix_modify documentation.

Thank you for the clarification.