Unitary step function including harmonic potential

Hello Sir,
Can we set unitary step function including this potential by Lammps command? or does it require source code changing?

harmonic potential,
V = -k(rc−r)Θ(rc-r)
where Θ is the unitary step function,

This is just a fancy mathematical way for applying a cutoff.

What is available is listed in the manual. If not, you can either try to approximate it with tabulation or implement it in C++.

Thank youn sir