Atom-wise search corresponds to the generation of newly fragmented molecules in the Expansion step of MCTS in the fragment-wise search (Fig. ). One path corresponds to one fragment by assigning one atom to one node. In one step, a new atom and the bonds associated with that atom are predicted to be added to the fragment in the intermediate state. Atoms that cannot be further bonded are excluded, considering the valence rule in the Expansion step. Atom-wise MCTS is executed as one cycle of the following process.