An important underlying assumption in ChemPer is that the molecular fragments have already been clustered by force field parameter. In this work, we use established force fields to cluster molecular fragments and then generate SMIRKS for those clusters. For example, all bonds which are assigned the same force constant and equilibrium bond length could be clustered together. Determining the appropriate combination of clustering algorithms with ChemPer will require more research. For now, we focus on the problem of how to generate SMIRKS patterns for groups of fragments.