Density-functional study of oxygen adsorption on Mo(112)

Atomic oxygen adsorption on the Mo(112) surface has been investigated by means of first-principles total energy calculations. Among the variety of possible adsorption sites it was found that the bridge sites between two Mo atoms of the topmost row are favored for O adsorption at low and medium coverages. At about one monolayer coverage oxygen atoms prefer to adsorb in a quasi-threefold hollow sites coordinated by two first-layer Mo atoms and one second layer atom. The stability of a structural model for an oxygen-induced $p(2\times 3)$ reconstruction of the missing-row type is examined.Comment: 6 pages, 6 postscript figures, RevTe

Surface properties of the clean and Au/Pd covered Fe3_3O4_4(111): a DFT and DFT+UU study

The spin-density functional theory (DFT) and DFT+$U$ with Hubbard $U$ term accounting for on-site Coulomb interactions were applied to investigate structure, stability, and electronic properties of different terminations of the Fe$_3$O$_4$(111) surface. All terminations of the ferrimagnetic Fe$_3$O$_4$(111) surface exhibit very large (up to 90%) relaxations of the first four interlayer distances, decreasing with the oxide layer depth. Our calculations predict the iron terminated surface to be most stable in a wide range of the accessible values of the oxygen chemical potential. The adsorption of Au and Pd on two stable Fe- and O-terminated surfaces is studied. Our results show that Pd binds stronger than Au both to the Fe- and O-terminated surface. DFT+$U$ gives stronger bonding than DFT. The bonding of both adsorbates to the O-terminated magnetite surface is by 1.5-2.5 eV stronger than to the Fe-terminated surface

The chemical potential for the inhomogeneous electron liquid in terms of its kinetic and potential parts with special consideration of the surface pote ntial step and BCS-BEC crossover

The chemical potential $\mu$ of a many-body system is valuable since it carries fingerprints of phase changes. Here, we summarize results for $\mu$ for a thre e-dimensional electron liquid in terms of average kinetic and potential energie s per particle. The difference between $\mu$ and the energy per particle is fou nd to be exactly the electrostatic potential step at the surface. We also prese nt calculations for an integrable one-dimensional many-body system with delta f unction interactions, exhibiting a BCS-BEC crossover. It is shown that in the B CS regime the chemical potential can be expressed solely in terms of the ground -state energy per particle. A brief discussion is also included of the strong c oupling BEC limit.Comment: 4 pages 3 figure

First-principles calculation of Li adatom structures on the Mo(112) surface

The formation and structure of the ordered phases of Li atoms adsorbed on the Mo(112) surface are investigated by performing first-principles density-functional calculations. Large inward relaxation for the first atomic interlayer distance of the clean Mo(112) surface is found. The vertical relaxations of the substrate are only little influenced by the adsorbed Li atoms. The magnitude of lateral shifts of atoms along the atomic rows is found to be small and in line with measured values. The energetics of chain structures of Li adatoms for coverages 0.125<~Θ<~1 monolayer is determined and the p(4×1) and p(2×1) adatom structures are found to be the most favored ones in agreement with experiment. The binding energy of Li atoms decreases with increasing coverage. The calculated work function changes with Li adatom coverage are in good agreement with experiment. The energy barriers for adatom diffusion are determined and the energetics of lateral interactions between adatoms is discussed.Peer reviewe

To what extent could acute general psychiatric day care reduce inpatient admissions?

The multi-site research project (Acronym: EDEN-study) “Psychiatric day hospital treatment: An alternative to inpatient treatment, being cost-effective and minimizing post-treatment needs for care? An evaluative study in European countries with different care systems” was funded by the European Commission (Quality of Life and Management of Living, contract no. QLG4-CT-2000-01700). Additional national grants supporting the project were provided by Roland-Ernst-Stiftung für Gesundheitswesen and the Faculty of Medicine at the Dresden University of Technology, the National Health Service Executive Organization and Management Programme, the Polish National Committee of Scientific Affairs, and the Slovak Ministry of Education. Pfizer Pharmaceutical Company supported travel and accommodation for EDEN project meetings

Energetics of metal slabs and clusters: the rectangle-box model

An expansion of energy characteristics of wide thin slab of thickness L in power of 1/L is constructed using the free-electron approximation and the model of a potential well of finite depth. Accuracy of results in each order of the expansion is analyzed. Size dependences of the work function and electronic elastic force for Au and Na slabs are calculated. It is concluded that the work function of low-dimensional metal structure is always smaller that of semi-infinite metal sample. A mechanism for the Coulomb instability of charged metal clusters, different from Rayleigh's one, is discussed. The two-component model of a metallic cluster yields the different critical sizes depending on a kind of charging particles (electrons or ions). For the cuboid clusters, the electronic spectrum quantization is taken into account. The calculated critical sizes of Ag_{N}^{2-} and Au_{N}^{3-} clusters are in a good agreement with experimental data. A qualitative explanation is suggested for the Coulomb explosion of positively charged Na_{\N}^{n+} clusters at 3<n<5.Comment: 11 pages, 6 figures, 1 tabl

Energetics of Sr adatom interactions on the Mo(112) surface

First-principles methods are used to investigate the formation and structure of the ordered phases of Sr atoms adsorbed on the furrowed Mo(112) surface. The energetics of various commensurate and incommensurate adatom structures providing information on lateral interactions between adatoms is determined for coverages 0.11⩽Θ⩽1 monolayer. It is found that the binding energy of Sr atoms decreases with increasing coverage. The experimentally observed p(8×1) and p(5×1) adatom chains are found to belong to the most favored structures for Θ<0.5. The energetic difference between these two structures amounts to 20meV. The experimental work function variation with Sr adatom coverage is very well reproduced. The energy barriers for Sr diffusion along the atomic troughs are calculated and discussed.Peer reviewe

Oxidation of Mg(0001): A combined Experimental and Theoretical Study

The oxidation of magnesium proceeds in several stages, beginning with the oxygen dissociation process and ending with the formation of magnesium oxides. Our focus is on the intermediate oxidation state at the Mg(0001) surface, whose geometrical structure is an unsettled problem. By combining the results of high-accuracy electronic structure calculations with angle-scanned x-ray photoelectron diffraction measurements we are able to unambiguously determine the structure of the Mg(0001) surface upon oxidation. In contrast to previous studies of Mg(0001) oxidation and unlike the case of aluminum oxidation we find a rather unanticipated surface oxide structure, consisting of two mixed oxygen-magnesium layers on top of an almost undisturbed Mg(0001) surface. This unusual surface oxide structure is locally formed already at very low coverages of 0.1 monolayer and grows laterally with increasing oxygen coverage up to 2 monolayers