To explore adatom effects on enantiospecific lateral interactions, like and unlike [6]H dimers were placed side by side over one-and three-adatom Cu substrates. In the initial dimer structures, one enantiomer was directly above the adatom, while the other was nearby but above the portion of the substrate without the adatoms. We found that the configurational space sampled by helicene dimers was even larger than what was available in the case of monomer binding, and standard algorithms for DFT-based structural optimization led to multiple metastable states close in geometry to the initial structures. To better understand the configurational space, AIMD calculations were carried out for xxx ps. The movies in the SI (MM_1ad.mp4, MP_1ad.mp4 and MP_3ad.mp4) show the trajectories of like and unlike dimers on one-and three-adatom surfaces. Representative snapshots were selected from each simulation, and zero-Kelvin optimizations were carried out in order to determine binding energies. The energies corresponding to the most stable configurations are reported in Table , and corresponding minimum energy structures are presented in Figures and. *The first molecule indicated in each pair was placed above the adatoms in the initial structure. Surface interactions drove assembly in all of the lateral dimer calculations. Because of the limited defect footprint on one-adatom surfaces, a single molecule was bound to the adatom in these cases. The second molecule experienced the type of flattening observed in monomers deposited on pristine substrates. On three-adatom substrates, both adsorbates were able to bind to the adatoms, and adatom migration was observed where this facilitated binding. As for monomers, three-adatom binding was stronger than one-adatom binding. Binding energies per molecule, however, are in the same range as monomer binding energies, suggesting that lateral interactions, including enantiospecific interactions, negligible in this case.