where Φ Φ 12 ( r ) is the interatomic potential between atom i and atom j, ϵ ϵ is the minimum potential energy, α α is the measurement of the repulsive energy steepness which is the ratio σ σ / r m i n , σ σ is the value of r where Φ Φ 12 ( r ) is zero, and r m i n is the value of r which can achieve the minimum interatomic potential ϵ ϵ . This potential function is only valid when r > r m a x , as the potential will decay towards − − ∞ ∞ as r → → 0 . This is corrected by identifying r m a x , which is the value of r at which the potential is maximized; when r ≤ ≤ r m a x , the potential is set to infinity.