Here, r is the interatomic distance, rc is the cut-of dis-
tance, and and are the potential parameters that de-
termine the equilibrium interatomic distance and the bind-
ing energy. The second and third terms in the first equa- tion are modification terms that were added to enforce the continuity of the energy and the interatomic force at
r = rc. The equilibrium interatomic distance r0 that gives
the minimum energy between an atomic pair is calculated
as r0 = 21/6.
Series A, Vol. 49, No. 4, 2006