someone knows the physical meanings of the bond coeff command in the atom_style gran

Hi, I have a question, I know that in LIGGGHTS WITH BONDS there are two forms of fracture, my doubt is that it means that value of " $c " y {" rb "}
variable rp equal 0.015625 #Radio de la particula
variable d equal 2*${rp} #Diametro de la particula
variable rb equal 0.8*${rp} **************************** What happens physically if I increase this value?
variable I equal 0.25*PI*${rb}*${rb}*${rb}*${rb}
variable A equal PI*${rb}*${rb}
variable kn equal 2*$Y/$d # comportamiento del grano 3.2e8 tesis 1e10
variable ks equal 12*$I*$Y/($A*$d*$d*$d) #${kn}/2.5

variable simplebreak equal 0
variable stressbreak equal 1

bond_coeff 1 ${rb} $Y $G ${simplebreak} $c #******************* what physical meaning has the value of c?
bond_coeff 1 ${rb} ${kn} ${ks} ${stressbreak} $A $B # A= sigma_rupture_compression y B= A= sigma_rupture_shear, it is right ?

####I understand that "stressbreak" allows the fracture if a rupture sigma is exceeded, but I do not understand the "simplebreak"
what does simplebreak mean?