Density Functional Study on the Stability and Reactivity of Pt(100) and Pt(111) Surfaces Modified by Ni Atoms

DFT study on the the stability and reactivity of Pt(100) and Pt(111) surfaces modified by nickel UPD monolayer deposition have been carried out. We used the binding energy calculation of bimetallic structures versus the cohesion energy of the bulk adsorbate to quantify the underpotential shift (ΔEupd) to determine the stability of the bimetallic systems. The reactivity of the clean and modified surface was analized by energy levels of the highest occupied molecular orbital (HOMO), softness and local softness. We concluded that the stability of Pt(100)25Ni9 and Pt(111)25Ni10 bimetallic structures cannot be explained by excess of the metal- substrate binding energy but the instability can be explained by structural effects. We found that the modified surfaces are more reactive and the active sites are located in the centre of the cluster which favores the formation of islands of atoms onto these surfaces

Geometrical-topological correlation in structures

The topology of polyhedra, tessellations and networks is described as to their mapping in Schlaefli space. A description of the topological form index is given and it is applied to these structural classes in terms of their geometries

On the Hydrides of B, C, N, O and F

This paper reports a productive discussion of bonding principles in the non-metallic 2nd row hydrides. It suggests the inversion of a bonding character, potentially from hydrides of B & C, which may display unsaturation and electronic deficiency accompanied by electronic delocalization in 1D or 2D or 3D. Contrasted with the opposite possibility, within the finite number of hydrides of N, O and F, that display apparently extensive H-bonding and subsequently proton delocalization in 1D and 2D (in HF & ice polymorphs, respectively), and now potentially in 3D in a corresponding hydride of N called Rice's blue material, or perhaps polyimidogen. Where polyimidogen is a crystalline NH lattice that is a polymorph of the ammonium azide structure-type thus

The carbon allotrope glitter as n-diamond and i-carbon nanocrystals

Diffraction data taken from nanocrystalline n-diamond and i-carbon forms is fit to a so-called glitter model, in which the geometry of the C lattice has been optimized by density functional theory (DFT). A calculated theoretical diffraction pattern for glitter is shown to be a close fit to the experimental data for these novel C forms

Financial Dollarization and the Size of the Fear

Based on the significance of a Minimum Variance Portfolio (MVP) for the understanding of dollarization equilibria, a significant strand of the debate concerned with the driving forces behind this phenomenon has focused on analyzing the determinants of the relative volatility of inflation vis-à-vis real depreciation. This analysis contributes in the identification of those factors by extending the basic CAPM formulation via the introduction of credit risk that is directly linked to the shock that determines real returns for dollar denominated assets: unanticipated shifts in the real exchange rate. We show this ingredient can end up altering the perceived relative volatility of peso and dollar assets in a way that fuels financial dollarization (by increasing the relative hedging opportunities offered by the latter). We calibrate our model using Peruvian data for the period 1998-2004, and its predictions show a better fit with observed financial dollarization ratios than those of the basic CAPM model.Financial dollarization, Minimum Variance Portfolio, Peru

Algebraic solution of a graphene layer in a transverse electric and perpendicular magnetic fields

We present an exact algebraic solution of a single graphene plane in transverse electric and perpendicular magnetic fields. The method presented gives both the eigen-values and the eigen-functions of the graphene plane. It is shown that the eigen-states of the problem can be casted in terms of coherent states, which appears in a natural way from the formalism.Comment: 11 pages, 5 figures, accepted for publication in Journal of Physics Condensed Matte