A Minimal Cluster Model of Valence Electrons in Adatom-Assisted Adsorbed Molecules: NCH3/Cu(110) and OCH3/Cu(110)

In this study, we found that the local density of states and ionization energy spectrum of the valence electrons of methylnitrene (NCH3) adsorbed on Cu(110) can be calculated from molecular orbital calculations of a simple artificial isolated NCH3–Cu2 molecular cluster in which the two Cu atoms form bonds to the N atom. Such a NCH3–Cu2 cluster represents the basic structural unit of a NCH3 molecule adsorbing on a Cu double-added-row structure. This finite NCH3–Cu2 cluster structure is not optimized as a single system but is extracted directly from an optimized surface structure obtained by density functional theory with periodic boundary conditions. With this approach, we obtained excellent agreement between the measured ultraviolet photoemission spectra (UPS) and the theoretical calculation results. To further examine this minimal cluster concept, we analyzed methoxy (OCH3) adsorption on Cu(110) and found a OCH3–Cu3 cluster structure. On the basis of this structure, we calculated UPS and also obtained su...