Hi Manish,
You are keeping the LJ interactions for AIREBO but reducing the cut-off of the potential to 1.7 sigma; this will create errors. The LJ interactions are not well-defined for separations < 2 Angstroms. The potential was parameterized for a fixed cut-off of 3 sigma; you shouldn’t modify it unless you have a good reason. Try increasing your cut-off or removing the LJ terms and see if your error persists.
Best,
Thomas C. O’Connor
Ph.D. Candidate
Dept. of Physics & Astronomy
Johns Hopkins University