Band structure of Au layers on the Ru(0001) and graphene/Ru(0001) surfaces

The electronic structures of Au monolayers on the Ru(0001) and graphene-coated Ru(0001) surfaces have been calculated by DFT method using the supercell (repeated-slab) approach. The local densities of states (LDOS) and band structures of the monolayer and bilayer Au films adsorbed on the graphene/Ru(0001) and those of free hexagonal Au layers are found to be very similar. This result indicates that the monolayer graphene almost completely screens the Au layers from the Ru(0001) substrate surface, so that electronic properties of Au films adsorbed on graphene are determined predominantly by the electronic structure of the Au adlayers, essentially independent on the electronic structure of the substrate surface

Model of the CO oxidation reaction on Au-covered Mo(112)

The adsorption of O and CO and the CO oxidation reaction on the Au-covered Mo(112) surface have been studied by means of DFT calculations of binding and activation energies. As follows from previous studies [K. Fukutani et al., Appl. Surf. Sci. 256, (2010) 4796], adsorbed Au atoms create rods lying in the furrows of the Mo(112) surface. Due to a furrowed structure of the Mo(112), a p(1 × 1)Au monolayer does not cover the surface completely, and Mo atomic rows remain available for oxygen adsorption. It is found that oxygen adsorbs dissociatively on these Mo substrate atoms. In turn, CO molecules prefer adsorption sites on the Au rows atop Au atoms, so that CO and oxygen do not hinder each other from adsorption. The Au coating significantly decreases the binding energy of O on the Mo(112) surface. This feature is essential for the lowering of the barrier for CO oxidation, which is found to be as low as 0.19 eV. In presence of adsorbed O, the binding energy of CO is relatively small (0.29 eV), but increases to 0.64 eV when CO adsorbs on bilayer Au films. Hence, the p(1 × 4) and p(1 × 3) Au bilayer structures on Mo(112) surface are predicted to be efficient catalysts for CO oxidation

The influence of both coordination number and lattice constant on the nonmetal to metal transition

We show that both coordination and lattice constant can have an important influence on the nonmetal to metal transition and the two parameters are not easily separated. Using example theoretical calculations for barium, we provide a compelling case that atomic coordination is a critical factor in determining the critical lattice constant for the nonmetal to metal transition. A comparison between the nonmetal to metal transition three-dimensional and two-dimensional systems is not possible on the basis of the atomic coordination alone. This is discussed in the context of a comparison of the available experimental data for both elemental expanded fluids (three-dimensional) and overlayers (quasi-two-dimensional)

DFT calculations of the electronic structure of SnO

The electronic structures of Sn and SnOx layers adsorbed on the Pd(110) surface have been calculated by DFT. In agreement with available results of photoemission studies, it is found that the formation of the oxides induces pronounced changes in the related peak in the DOS. In particular, it is shown that the formation of SnO2 adsorbed layers leads to a transformation of the Sn 4d spin-orbit doublet into a quadruple peak, while for SnO the peak retains its shape. Due to this feature, the shape of the Sn 4d peak in photoemission spectra can serve as an unambiguous indicator of the degree of oxidation of Sn layers on transition metal surfaces

Metallization and stiffness of the Li-intercalated MoS2 bilayer

Performed density-functional theory (DFT) calculations have shown that the Li adsorption on the MoS2 (0 0 0 1) surface, as well as Li intercalation into the space between MoS2 layers, transforms the semiconductor band structure of MoS2 into metallic. For the (√3 × √3) – R30° Li layer, the band structures of the MoS2 bilayer with adsorbed and intercalated Li are very similar, while for higher Li concentrations, the character of metallization for the adsorbed layer substantially differs from that of the MoS2–Li–MoS2 layered system. In particular, for the adsorbed (1 × 1) Li monolayer, the increased density of the layer leads to the nonmetal-to-metal transition, which is evident from the appearance of the band crossing EF with an upward dispersion, pertinent to simple metals. It has been demonstrated that intercalated Li substantially increases the interlayer interaction in MoS2. Specifically, the estimated 0.12 eV energy of the interlayer interaction in the MoS2 bilayer increases to 0.60 eV. This result is also consistent with results of earlier DFT calculations and available experimental results for alkali-intercalated graphene layers, which have demonstrated a substantial increase in the stiffness due to intercalation of alkalis