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 substantial agreement with the experimental UPS. These results may indicate that, when substrate adatoms bridge the adsorption of a molecule and a surface, a small cluster consisting of the adsorbate and the neighboring bonding substrate adatoms suffices to describe the electronic structure of the valence electrons of the adsorbates

Scanning Tunneling Microscopy and Density Functional Theory Studies of Adatom-Involved Adsorption of Methylnitrene on Copper(110) Surface

In this study, we used scanning tunneling microscopy (STM) and density functional theory (DFT) to examine the bonding structure of CH₃N adsorbed on the Cu(110) surface. A previous study [<i>Chin. J. Phys.</i> <b>2005</b>, <i>43</i>, 212–218] shows the adsorbed CH₃N aggregate to form a zigzag structure with a <i>p</i>(2 × 3) unit cell, without considering the possibility of adsorbate-induced surface reconstruction. Here, we propose a revised adsorption structure, with the key feature of bonding each CH₃N with two Cu adatoms in a tetrahedral manner. Three structure models (double-row, dimer, and alternative-dimer) are examined by ab initio calculations. We find that the most energetically favorable model is the double-row model with CH₃N bonding alternatingly along either side of double added rows from Cu adatoms