Finally, ab initio MD simulations were performed at 100 K to investigate the adsorption dynamics at site X. Across all three monolayers the adsorbed Cu atom migrates off site X in under 500 fs. After this, the Cu atom stays adsorbed at the H site on WS 2 , and M on WSe 2 and WTe 2 . This is consistent with similar stability on these sites and moderate activation barriers for Cu migration, and further shows that site X is not a stable adsorption site for a single metal atom.