The structure of the $\mathrm{C}_{60}$ monolayer on Pb(111)

Low-energy electron diffraction and scanning tunneling microscopy studies indicate that a monolayer of $\mathrm{C}_{60}$ on Pb(111) forms a modulated structure having an average $\mathrm{C}_{60}$-$\mathrm{C}_{60}$ nearest-neighbor distance of about 10\AA, but a period of about 46\AA. The data were analyzed in the context of the Tkatchenko method$\,^{\dag}$, and the monolayer structure was identified as two coexisting higher-order commensurate structures, namely $(\sqrt{169}\times \sqrt{169})R16.90\,^{\circ}$ and $(\sqrt{169}\times \sqrt{169})R21.31\,^{\circ}$, both with 21 $\mathrm{C}_{60}$ molecules and 169 Pb atoms in their unit cells. This modulated structure has implications for the electronic structure of the $\mathrm{C}_{60}$ film, as measured using scanning tunneling spectroscopy. \newline $\,^{\dag}$A. Tkatchenko, Phys. Rev. B 75, 235411 (2007).