In this work, we define the local structure of a non-terminal (central) atom as the relative geometry of the atoms connected to it. We use a breadth-fist algorithm to generate atomic labels. Atoms with higher atomic ranking (generated with RDkit ) and which are non-terminal have a preference to be selected as the next atom. Particularly, every time the algorithm reaches a non-terminal atom, it generates labels for all its non-labeled neighboring nodes. The non-terminal node and its neighbors form a group. In a group of atoms, the first atom is the central one. The next is the one that had been previously visited by the algorithm. Finally, the remaining atoms are added to the group based on their ranking. This is illustrated in Figure . We can specify the local structure within a group (g i ) as a set of internal coordinates. Distances between pairs of connected atoms ((i, k) with k ∈ g i ) are generated using the force field equilibrium distance parameters. Angles between triplets of atoms are set using the force field equilibrium angle parameter. Triplets of atoms are chosen using the atoms (j, i, k) in the group, where k ∈ g i and k > i. If g i has more than 3 atoms, dihedral angles are needed. Dihedral angles are assigned based on the hybridization of the central atom i.