β e α αβ exp -α r i j r m,i j -αe β αβ exp -β r i j r m,i j (2) Here, the parameters ε i j and r m,i j have exactly the same physical interpretation as in the LJ functional form (eq 1). The two extra parameters, α and β , control the steepness of the repulsive interaction and decay of the attractive interaction, respectively, thus offering control over the shape of the potential energy well . An additional advantage of the DE potential is its natural soft core, which ensures that the energy is finite at r = 0: