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We studied the adsorption state of dimethyl disulfide and methylthiolate on the Au(111) surface by means of the density functional theory (DFT) within a generalized gradient approximation and experimental high-resolution electron energy loss spectroscopy (HREELS) techniques. It turns out that the methylthiolate adsorption is more stable than the dimethyl disulfide adsorption and that the most stable adsorption site for the methylthiolate is the bridge site slightly off-centered towards the fcc-hollow site with its S–C bond tilted from the surface normal by 53°. HREELS results are in excellent agreement with the DFT results, providing very strong support to the depicted adsorption scenario.

We investigate the spin-and energy dependent tunneling through a single organic molecule (CoPc) adsorbed on a ferromagnetic Fe thin film, spatially resolved by low-temperature spin-polarized scanning tunneling microscopy. Interestingly, the metal ion as well as the organic ligand show a significant spin-dependence of tunneling current flow. State-of-the-art ab initio calculations including also van-der-Waals interactions reveal a strong hybridization of molecular orbitals and surface 3d states. The molecule is anionic due to a transfer of one electron, resulting in a non-magnetic (S= 0) state. Nevertheless, tunneling through the molecule exhibits a pronounced spin-dependence due to spin-split molecule-surface hybrid states. [4,5]. However, detailed and quantitative access to different constituents of a single molecule is desirable, though challenging. Scanning tunneling microscopy (STM) is well established as a probe of a local spin [6][7][8][9][10][11][12][13] in an atomically well defined environment.Iacovita et al. recently performed a spin-polarized STM (SP-STM) study of a CoPc in contact with a ferromagnetic cobalt nano-island [14]. Stacking contrast, spin-dependent scattering, edge states, mesoscopic relaxations as well as the adsorbate induced modification create a complex environment [15] toward understanding the influence of the substrate on molecular magnetism. After careful selection of electronically equivalent Co nanoislands a ferromagnetic exchange interaction between the molecular spin and the cobalt lead was successfully deduced, both theoretically and experimentally.In this letter we demonstrate a significant spinpolarization for a CoPc molecule in contact with a ferromagnetic Fe thin film due to molecule-substrate hybridization even though the molecule loses its net spin. As confirmed by SP-STM, an energy/site-dependent spin polarization from inversion to amplification is resolved on the sub-molecular scale. State-of-the-art density functional theory (DFT), which includes the decisive role of van-der-Waals (vdW) interactions, reveals both the magnetic and electronic nature of the molecule coupled to the ferromagnetic substrate. Even though the net spin of the molecule is lost due to a transfer of one electron, spin-splitting is recovered through the local bonding of molecular orbitals with Fe 3d bands.Simulations were carried out in the DFT [16] formalism with a plane wave implementation as provided by the VASP code [17]. Pseudopotentials used were generated with the projector augmented wave method [18] by using the PBE generalized-gradient exchange-correlation energy functional [19] (GGA). A slab consisting of two Fe and three W atomic layers, with a (5×7) in-plane surface unit cell modeled the molecule-surface system. The kinetic energy cutoff of the plane waves was set to 500 eV while the Brillouin zone was sampled by the Γ point. Optimized molecule-surface geometries were obtained by relaxing all molecular degrees of freedom and those of the Fe overlayers by including long-range vdW intera...

The interaction of water with oxide surfaces has drawn considerable interest, owing to its application to problems in diverse scientific fields. Atomic-scale insights into water molecules on the oxide surface have long been recognized as essential for a fundamental understanding of the molecular processes occurring there. Here, we report the dissociation of a single water molecule on an ultrathin MgO film using low-temperature scanning tunnelling microscopy. Two types of dissociation pathway--vibrational excitation and electronic excitation--are selectively achieved by means of injecting tunnelling electrons at the single-molecule level, resulting in different dissociated products according to the reaction paths. Our results reveal the advantage of using a MgO film, rather than bulk MgO, as a substrate in chemical reactions.