where U ab (r) k , g ab (r) k , and g ab (r) AA are the potential energy function, RDF at the k th iteration, and the target atomistic RDF, respectively, for the pair of CG beads of type a and b. T is the simulation temperature, k B is the Boltzmann constant, and α is a damping coefficient. The second term on the RHS goes to zero as the CG RDF (g(r) k-1 ) approaches the target RDF (g(r) AA ). Pair-wise interactions between beads separated by less than four bonds were excluded. In the case of IBI PC , an additional attractive potential correction of the form