These parameters are additive over atom pairs (i.e., the energy between two molecules is the sum of the pairwise atom interaction energies), which is common for most classical force fields . This additivity makes atomistic generation efficient. We also emphasize that the CBMC-like approach we follow requires this property to ensure the accuracy of the Rosenbluth method in generating stable configurations of the molecule as ∆E (change in energy) is computed per atom and its energy contribution should not change irrespective of the atoms added later on. v ) Recoil. An intermediate state during the generation phase is called a dead-end if placing the atom is necessary to satisfy the requirements of a particular atom-type, but it cannot be placed without having it clash (overlap of the van der Waals radii) with either the protein or the molecule itself. For example, this could be when a carbonyl carbon atom is placed, but any possible place to put the oxygen atom would clash with the protein. To avoid such dead-ends, the algorithm checkpoints the growth at every stage where the rules for every atom-type are satisfied (i.e., when all six atoms of a benzene ring or both the carbon and oxygen atom in a carbonyl group have been placed).