Elena Voloshina

Induced magnetism of carbon atoms at the graphene/Ni(111) interface

We report an element-specific investigation of electronic and magnetic properties of the graphene/Ni(111) system. Using x-ray magnetic circular dichroism, the occurrence of an induced magnetism of the carbon atoms in the graphene layer is observed. We attribute this magnetic moment to the strong hybridization between Cu2009π and Niu20093d valence band states. The net magnetic moment of carbon in the graphene layer is estimated to be in the range of 0.05–0.1u2002μB per atom.

Graphene on metallic surfaces: problems and perspectives

The present manuscript summarizes the modern view on the problem of the graphene-metal interaction. Presently, the close-packed surfaces of d metals are used as templates for the preparation of highly-ordered graphene layers. Different classifications can be introduced for these systems: graphene on lattice-matched and graphene on lattice-mismatched surfaces where the interaction with the metallic substrate can be either strong or weak. Here these classifications, with the focus on the specific features in the electronic structure in all cases, are considered on the basis of large amount of experimental and theoretical data, summarized and discussed. The perspectives of the graphene-metal interfaces in fundamental and applied physics and chemistry are pointed out.

Structural and electronic properties of the graphene/Al/Ni(111) intercalation system

Decoupling of the graphene layer from the ferromagnetic substrate via intercalation of sp metal has recently been proposed as an effective way to realize a single-layer graphene-based spin-filter. Here, the structural and electronic properties of the prototype system, graphene/Al/Ni(111), are investigated via a combination of electron diffraction and spectroscopic methods. These studies are accompanied by state-of-the-art electronic structure calculations. The properties of this prospective Al-intercalation-like system and its possible implementations in future graphene-based devices are discussed.

Graphene on ferromagnetic surfaces and its functionalization with water and ammonia

In this article, an angle-resolved photoelectron spectroscopy (ARPES), X-ray absorption spectroscopy (XAS), and density-functional theory (DFT) investigations of water and ammonia adsorption on graphene/Ni(111) are presented. The results of adsorption on graphene/Ni(111) obtained in this study reveal the existence of interface states, originating from the strong hybridization of the graphene π and spin-polarized Ni 3d valence band states. ARPES and XAS data of the H2O (NH3)/graphene/Ni(111) system give an information regarding the kind of interaction between the adsorbed molecules and the graphene on Ni(111). The presented experimental data are compared with the results obtained in the framework of the DFT approach.

Local correlation method for metals: Benchmarks for surface and adsorption energies

Highly accurate methods such as coupled cluster (CC) techniques can be used for periodic systems within the framework of the method of increments. Its extension to low-dimensional conducting system is considered. To demonstrate the presented approach a clean Mg (0001) surface is selected, where the CC treatment with single and double excitations and perturbative triples is used for calculation of the surface energy. Further example concerns the adsorption energy of Xe on the metal surface. The obtained results can be used to verify performance of the approximate methods. Along with the computational speed-up at the high-level of accuracy, application of the method of increments provides for a possibility to analyze influence of individual correlation-energy increments on the studied property.

Accurate quantum‐chemical description of gold complexes with pyridine and its derivatives

Interaction of gold with pyridine and its derivatives was studied by means of different wavefunction‐based correlation methods and standar DFT functionals as well as accounting for dispersion correction. Comparison of the calculated binding energies with benchmark CCSD(T)results allows us to find an appropriate computational method, when considering the two structures reflecting the interaction of gold with the lone pair at nitrogen, on the one hand, and with the π‐system of pyridine, on the other hand. Additional binding sites were evaluated, when performing potential energy surface calculations and structure optimizations. The enhancement of the interaction energy due to donor substituents in the 4‐position of the pyridine molecule has been investigated.

Structural and electronic properties of Fe3O4/graphene/Ni(111) junctions

The Fe3O4(111)/graphene/Ni(111) trilayer is proposed to be used as an ideal spin-filtering sandwich where the half-metallic properties of magnetite are used. Thin magnetite layers on graphene/Ni(111) were prepared via successive oxidation of thin iron layer predeposited on graphene/Ni(111) and formed system was investigated by means of low-energy electron diffraction (LEED) and photoelectron spectroscopy (PES) of core levels as well as valence band. The electronic structure and structural quality of the graphene film sandwiched between two ferromagnetic layers remains unchanged upon magnetite formation as confirmed by LEED and PES

The role of electron correlations in the binding properties of Ca, Sr, and Ba.

In order to apply wavefunction-based correlation methods to solids it is necessary to have reliable Hartree-Fockxa0(HF) results for the infinite system of interest. We performed Hartree-Fock calculations for the group 2 heavy alkali-earth metals Ca, Sr, and Ba. For that, basis sets of valence-double-ζ quality have been optimized for the periodic systems. In all cases small-core pseudopotentials were used to deal with the scalar-relativistic effects. We determine the cohesive energies, the equilibrium volumes and the bulk moduli of the systems at the Hartree-Fock level and compare them with experimental data as well as the results of density functional theory calculations. Relativistic effects in the case of Ba are estimated by using a non-relativistic pseudopotential. The comparative HF versus the density functional theoryxa0(DFT) study of the electronic structures of Ca, Sr, and Ba has been performed.

Calculation of the X-Ray emission K and L 2,3 bands of metallic magnesium and aluminum with allowance for multielectron effects

A procedure is proposed to calculate the shape of the characteristic X-ray emission bands of metals with allowance for multielectron effects. The effects of the dynamic screening of a core vacancy by conduction electrons and the Auger effect in the valence band are taken into account. The dynamic screening of a core vacancy, which is known to be called the MND (Mahan-Nozeieres-De Dominics) effect, is taken into account by an ab initio band calculation of crystals using the PAW (projected augmented waves) method. The Auger effect is taken into account by a semiempirical method using the approximation of a quadratic dependence of the level width in the valence band on the difference between the level energy and the Fermi energy. The proposed calculation procedure is used to describe the X-ray emission K and L2,3 bands of metallic magnesium and aluminum crystals. The calculated spectra agree well with the experimental bands both near the Fermi level and in the low-energy part of the spectra in all cases.

Graphene on Rh(111)

The electronic and crystallographic structure of the graphene/Rh(111) moire lattice is studied via combination of density-functional theory calculations and scanning tunneling and atomic force microscopy (STM and AFM). Whereas the principal contrast between hills and valleys observed in STM does not depend on the sign of applied bias voltage, the contrast in atomically resolved AFM images strongly depends on the frequency shift of the oscillating AFM tip. The obtained results demonstrate the perspectives of application atomic force microscopy/spectroscopy for the probing of the chemical contrast at the surface.