Surface-induced magnetism in C-doped SnO2_{2}

The magnetism of C-doped SnO$_{2}$ (001) surfaces is studied using first-principles calculations. It is found that carbon does not induce magnetism in bulk SnO$_{2}$ when located at the oxygen site, but shows a large magnetic moment at the SnO$_{2}$ (001) surface. The magnetic moment is mainly contributed by the carbon atoms due to empty minority spins of $p$ orbitals and is localized at the surface and subsurface atoms. No magnetism is observed when the carbon atom is located at the subsurface oxygen sites. The origin of magnetism is discussed in the context of surface bonding.Comment: 3 pages, 3 figure

Current rectification in molecular junctions produced by local potential fields

The transport properties of a octane-dithiol (ODT) molecule coupled to Au(001) leads are analyzed using density functional theory and non-equilibrium Green functions. It is shown that a symmetric molecule can turn into a diode under influence of a local electric field created by an external charged probe. The origin of the asymmetry of the current--voltage ($I-V$) dependence is traced back to the appearance of a probe induced quasi--local state in the pseudogap of the ODT molecule. The induced state affects electron transport, provided it is close to the Fermi level of the leads. An asymmetric placement of the charged probe along the alkane chain makes the induced quasi--local state in the energy gap very sensitive to the bias voltage and results in rectification of the current. The results based on DFT are supported by independent calculations using a simple one--particle model Hamiltonian.Comment: 7 pages, 6 figure

Tuning the electrical conductivity of nanotube-encapsulated metallocene wires

We analyze a new family of carbon nanotube-based molecular wires, formed by encapsulating metallocene molecules inside the nanotubes. Our simulations, that are based on a combination of non-equilibrium Green function techniques and density functional theory, indicate that these wires can be engineered to exhibit desirable magnetotransport effects for use in spintronics devices. The proposed structures should also be resilient to room-temperature fluctuations, and are expected to have a high yield.Comment: 4 pages, 6 figures. Accepted in Physical Review Letter

On determining defects identity in carbon nanotubes using charge probes

A metallic carbon nanotube with point-like defects under influence of a local potential due to a point charge probe is theoretically studied. A combination of density functional theory and the Landauer-Büttiker formalism is used to compute the electronic conductance in the zero-voltage limit. From a collection of the results obtained by varying the probe position around different defects the conductance maps are created. The analysis of the conductance maps allows us to formulate conditions under which several point-like defects (the Stone-Wales defect, a simple carbon vacancy, hydrogen-passivated vacancies) can be distinguished and identified in experiments with the help of scanning probe microscopy.This work has been supported by the National Science Centre under the contract DEC-2012/07/B/ST3/03412. We acknowledge that the results of this research have been achieved using the PRACE-3IP project (FP7 RI-312763) resource JUROPA based in Germany at Julich. We also thank the Spanish MICINN for the Grant No. FIS2012-34858 (V.M.G.S. and J.F.) and the Ramón y Cajal Fellowship No. RYC-2010-06053 (V.M.G.S.).Peer Reviewe

A Discussion on Fall Detection Issues and Its Deployment: When cloud meets battery

IEEE International Conference on Cloud Computing and Big Data Analysis (3rd. 2018., Chengdu, China

Systematic pseudopotentials from reference eigenvalue sets for DFT calculations

Under a Creative Commons license.-- et al.Pseudopotential-based Density-Functional Theory (DFT) permits the calculation of material properties with a modest computational effort, besides an acknowledged tradeoff of generating and testing pseudopotentials that reproduce established benchmark structural and electronic properties. To facilitate the needed benchmarking process, here we present a pragmatic method to optimize pseudopotentials for arbitrary materials directly from eigenvalue sets consistent with all-electron results. This method thus represents a much needed pragmatic route for the creation and assessment of sensitive pseudopotentials for DFT calculations that has been exemplified within the context of the SIESTA code. Comprehensive optimized pseudopotentials, basis sets, and lattice parameters are provided for twenty chemical elements in the bulk, and for both LDA and GGA exchange–correlation potentials. This method helps addressing the following issues: (i) the electronic dispersion and structural properties for Ge, Pd, Pt, Au, Ag, and Ta better agree with respect to all-electron results now, (ii) we provide the expected metallic behavior of Sn in the bulk – which comes out semiconducting when using available pseudopotentials, (iii) we create a validated pseudopotential for LDA-tungsten, and (iv) we create the first Bi pseudopotential for SIESTA that reproduces well-known electron and hole pockets at the L and T points. We investigated the transferability of these pseudopotentials and basis sets, and predict a new phase for two-dimensional tin as well.P.R. and S.B.L. acknowledge partial support from the Arkansas Biosciences Institute. V.M.G.S. and J.F. acknowledge funding from the Spanish MICINN, Grant FIS2012-34858, and European Commission FP7 ITN “MOLESCO” (Grant No. 606728). V.M.G.S. thanks the Spanish Ministerio de Economía y Competitividad for a Ramón y Cajal fellowship (RYC-2010-06053), Y.Y. and L.B. thank ONR (Grants N00014-11-1-0384 and N00014-12-1-1034), and K.P. acknowledges funding from the National Science Foundation (DMR-1206354).Peer Reviewe

Heptagon-Containing Nanographene Embedded into [10]Cycloparaphenylene

We report the synthesis and characterization of a novel type of nanohoop, consisting of a cycloparaphenylene derivative incorporating a curved heptagon-containing π-extended polycyclic aromatic hydrocarbon (PAH) unit. We demonstrate that this new macrocycle behaves as a supramolecular receptor of curved π-systems such as fullerenes C60 and C70, with remarkably large binding constants (ca. 107 M−1), as estimated by fluorescence measurements. Nanosecond and femtosecond spectroscopic analysis show that these host-guest complexes are capable of quasi-instantaneous charge separation upon photoexcitation, due to the ultrafast charge transfer from the macrocycle to the complexed fullerene. These results demonstrate saddle-shaped PAHs with dibenzocycloheptatrienone motifs as structural components for new macrocycles displaying molecular receptor abilities and versatile photochemical responses with promising electron-donor properties in host-guest complexes.Junta de Andalucia-Consejeria de Universidad, Investigacion e Innovacion and FEDER(ERDF) "A way of making Europe" P18-FR-2877ERDF "A way of making Europe"Universidad de Granada / CBU

Short-term effects of a wildfire on the endangered Dupont’s Lark Chersophilus duponti in an arid shrub-steppe of central Spain

In Europe, Dupont’s Lark Chersophilus duponti is a threatened open-habitat bird. Prescribed burning has sometimes been proposed for its conservation, but without evidence of its effectiveness. To evaluate the short-term effects of a summer wildfire on this species, we performed several transect counts in the burnt and unburnt parts of a shrubsteppe in central Spain. The same transects were counted within a three-year interval prior to the fire and were repeated during the first two springs after the fire. We also measured the vegetation during the first two springs after the fire. In the burnt area, we observed a decrease of about 85–100% in Dupont’s Lark abundance, and about 7–15% in the control area. The disappearance of the scrub cover after fire and its slow regeneration, as well as the large increase in grass cover during the second year, may explain the decrease in this habitat-specialist bird species. Fire should be avoided in areas occupied by the Dupont’s Lark, as its negative effects in the short-term may cause local extinctions. However, prescribed burning may be used in neighboring areas to create new open habitats that may be subsequently colonized by this species.Peer Reviewe