996 research outputs found
Variation in Surface Energy and Reduction Drive of a Metal Oxide Lithium-Ion Anode with Stoichiometry: A DFT Study of Lithium Titanate Spinel Surfaces
No full textOpen data archive for "Variation in Surface Energy and Reduction Drive of a Metal Oxide Lithium-Ion Anode with Stoichiometry:
A DFT Study of Lithium Titanate Spinel Surfaces" by B. J. Morgan, J. Carrasco and G. Teobaldi. J Mater. Chem. A 4, 17180 (2016) doi:10.1039/c6ta05980eREADME.md file included in datase
Density functional theory screening of gas-treatment strategies for stabilization of high energy-density lithium metal anodes
No full textTo explore the potential of molecular gas treatment of freshly cut lithium foils in non-electrolyte-based passivation of high-energy-density Li anodes, density functional theory (DFT) has been used to study the decomposition of molecular gases on metallic lithium surfaces. By combining DFT geometry optimization and Molecular Dynamics, the effects of atmospheric (N2, O2, CO2) and hazardous (F2, SO2) gas decomposition on Li(bcc) (100), (110), and (111) surfaces on relative surface energies, work functions, and emerging electronic and elastic properties are investigated. The simulations suggest that exposure to different molecular gases can be used to induce and control reconstructions of the metal Li surface and substantial changes (up to over 1 eV) in the work function of the passivated system. Contrary to the other considered gases, which form metallic adlayers, SO2 treatment emerges as the most effective in creating an insulating passivation layer for dosages ≤1 mono-layer. The substantial Li → adsorbate charge transfer and adlayer relaxation produce marked elastic stiffening of the interface, with the smallest change shown by nitrogen-treated adlayers
Contrast stability and 'stripe' formation in scanning tunnelling microscopy imaging of highly oriented pyrolytic graphite: The role of STM-tip orientations
No full textHighly oriented pyrolytic graphite (HOPG) is an important substrate in many technological applications and is routinely used as a standard in Scanning Tunnelling Microscopy (STM) calibration, which makes the accurate interpretation of the HOPG STM contrast of great fundamental and applicative importance. We demonstrate by STM simulations based on electronic structure obtained from first principles that the relative local orientation of the STM-tip apex with respect to the HOPG substrate has a considerable effect on the HOPG STM contrast. Importantly for experimental STM analysis of HOPG, the simulations indicate that local tip-rotations maintaining a major contribution of the d3z2-r2 tip-apex state to the STM current affect only the secondary features of the HOPG STM contrast resulting in 'stripe' formation and leaving the primary contrast unaltered. Conversely, tip-rotations leading to enhanced contributions from m ≠ 0 tip-apex electronic states can cause a triangular-hexagonal change in the primary contrast. We also report a comparison of two STM simulation models with experiments in terms of bias-voltage-dependent STM topography brightness correlations and discuss our findings for the HOPG(0 0 0 1) surface in combination with tungsten tip models of different sharpnesses and terminations
Simulation of some dynamical aspects of the photophysics of dye molecules encapsulated in a dendrimer
No full textTermination effects in aluminosilicate and aluminogermanate imogolite nanotubes: A density functional theory study
No full textWe investigate termination effects in aluminosilicate (AlSi) and aluminogermanate (AlGe) imogolite nanotubes (NTs) by means of semi-local and range-corrected hybrid Density Functional Theory (DFT) simulations. Following screening and identification of the smallest finite model capable of accommodating full relaxation of the NT terminations around an otherwise geometrically and electrostatically unperturbed core region, we quantify and discuss the effects of physical truncation on the structure, relative energy, electrostatics and electronic properties of differently terminated, finite-size models of the NTs. In addition to composition-dependent changes in the valence (VB) and conduction band (CB) edges and resultant band gap (BG), the DFT simulations uncover longitudinal band bending and separation in the finite AlSi and AlGe models. Depending on the given termination of the NTs, such longitudinal effects manifest in conjunction with the radial band separation typical of fully periodic AlSi and AlGe NTs. The strong composition dependence of the longitudinal and radial band bending in AlSi and AlGe NTs suggests different mechanisms for the generation, relaxation and separation of photo-generated holes in AlSi and AlGe NTs, inviting further research in the untapped potential of imogolite compositional and structural flexibility for photo-catalytic applications
Understanding the cosolvation effect of dendrimers
No full textMolecules that are virtually insoluble in certain solvents may be uploaded to "hostile" phases by dendrimers. Prime examples of this phenomenon are Eosin Y, EY, and Rose Bengal, RB, that are not soluble in CH2Cl2 where they can, however, be solvated through the interaction with a fourth generation dendrimer of polypropylene amine, POPAM-4D. The two dyes share the same carbon framework and differ for the pattern of halogenation, and yet their cosolvation varies over a factor of 4: six Eosin Y and similar to 25 Rose Bengals are solvated by the macromolecule. Leveraging on a previous report where molecular dynamics simulations of 12 EY@ POPAM-4D in CH2Cl2 showed a reduction to the experimental limit of 6, we now perform similar calculations with an excess, i.e., 40, of RB@POPAM-4D. The simulations quantitatively reproduce the cosolvation effect. They also provide a microscopic understanding of its origin and of motions-interactions of the macromolecule and both of its guests
El Tlacuache Núm. 442 (2010). 442 Año 10 (2010) noviembre. El Tlacuache
No full textIronías en la historia de las ideas De diestros y siniestros por Fanny Campillo. -Tesis en torno a la autonomía de los pueblos indios por Gilberto López y Rivas
El Tlacuache Núm. 388 (2009). 388 Año 9 (2009) noviembre. El Tlacuache
No full textEl impacto de la Revolución Cubana en América Latinatados por Gilberto López y Rivas. - Del Tlalocan: uno de los reinos de los muertos por Isabel Garza Gómez
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