Reax Energy function

Hello all,
I am interested to know about any available documentation regarding mathematical description of bond-energy as a function of bond distance through bond order for Reax force field. I have gone through the main article “The ReaxFF reactive force-field: development, applications and future directions”. If anybody knows about any other reference to get the energy equation, I would like to request if that can be shared. Thanks a lot.
Yours Truly
Anubhav Roy

look for original paper ReaxFF: A Reactive Force Field for Hydrocarbons