The effect of defects on the electronic structure and magnetic map of the Fe<Subscript>2</Subscript>CrSi Heusler alloy: ab-initio calculations

Density functional theory (DFT) calculations are performed using the full-potential linearized augmented plane wave (FP-LAPW) and generalized gradient approximation (GGA) to study the electronic and magnetic properties of perfect and defected Fe₂CrSi Heusler alloy. The perfect structure was found to be a half-metallic ferromagnet with a total magnetic moment of 2 μ _B and a band gap 0.6 eV. The Fermi level is found to be in the middle of this gap, which is promising for fabricating tunneling magnetoresistance (TMR) devices. Among the studied defected structures Fe_Si and Cr_Si antisite defects as well as Fe-Si and Cr-Si defects destroyed the half metallicity. However the remaining antisite, swap and vacancy defects retained the half metallicity with band gaps lower than the perfect case.     

On the higher dimension Boussinesq equation with nonclassical condition

This paper deals with the solvability and uniqueness of a higher dimension mixed nonlocal problem for a Boussinesq equation. Galerkin's method was the main used tool for proving the solvability of the given nonlocal problem. Copyright © 2010 John Wiley & Sons, Ltd.     

Prediction of structural and thermodynamic properties of three products: 1-bromobenzene, tetrachlorethylene and 4-hydroxy-chromen-2-one using numerical methods

Our work concerns interaction spherical study of three toxic products, bromobenzene, tetrachloroethylene, and 4-hydroxy-chromene-2-one; using the Leap Frog algorithm, we calculated new values of cut-off of the box through Lennard-Jones potential parameters. This model was adapted to allow the determination of the characteristics for the SP₁, SP₂ and SP₃ state points and was applied to study the properties for the three products by molecular dynamics. This method provides an advantage to confirm the structure–activity relationship for these compounds. We calculated the thermodynamic and structural properties for both canonical NVT and isothermal–isobaric NPT ensembles of these products. Numerical system results have been compared with both experimental data and recent investigation theoretical. Our simulation model isobaric–isothermal system gives accurate results, and comparing with the canonical system, this model agrees very well with the experimental data. We aim to demonstrate that the classical approach with a low statistical uncertainty for liquid toxic leads to data in very good agreement with experiment or other types of calculations. We obtained a good prediction of the thermodynamic properties. We hope that this model with a lower threshold to 2.5σ could be an effective starting material for studying the properties of complex systems.     

‘Universal’ inequalities for the eigenvalues of the Hodge de Rham Laplacian

We obtain ‘universal’ inequalities for the eigenvalues of the Laplacian acting on differential forms of a Euclidean compact submanifold. These inequalities generalize the Yang inequality concerning the eigenvalues of the Dirichlet Laplacian of a bounded Euclidean domain.      

A note on solving Cauchy integral equations of the first kind by iterations

The successive approximation method was applied for the first time by N.I. Ioakimidis to solve practical cases of a Cauchy singular integral equation: the airfoil one. In this paper we study a more general case. We prove the convergence of the method in this general case. The proposed method has been tested for two kernels which are particularly important in practice. Finally, some numerical examples illustrate the accuracy of the method.     

A theoretical study of band structure properties for III–V nitrides quantum wells

Reliable and precise knowledge about the strain and composition effects on the band structure properties is crucial for the optimization of InGaN based heterostructures for electronic and optoelectronic device applications. AlInGaN as quaternary barrier material permits to control the band gap and the lattice constant independently. Using the model solid theory and the multi-band k.p interaction model, we investigate the composition effects on band offsets and band structure for pseudomorphic Ga_1−xIn_xN/Al_zIn_yGa_1−y−zN (0 0 1) heterointerfaces having zinc-blende structure. The results show that both conduction and valence band states are strongly modified while varying In and Al contents in the well and barrier materials. Furthermore, it is found that using AlInGaN as the barrier material allows the design of heterostructures including InGaN wells with tensile, zero or compressive strain. Such results give new insights for III-nitride compounds based applications and especially may guide the design of white-light emission diodes.     

Oscillation of second-order strongly superlinear and strongly sublinear dynamic equations

We establish some new criteria for the oscillation of second-order nonlinear dynamic equations on a time scale. We study the case of strongly superlinear and the case of strongly sublinear equations subject to various conditions.     

FTIR and thermal studies of modified natural rubber based polymer electrolytes

Chemical modification of natural rubber (NR) has frequently been attempted to improve the performance in specific application. 30% poly (methyl metacrylate) grafted NR (MG 30) has been explored as a potential candidate for polymer electrolytes. The complexation effect of LiCF₃SO₃, ethylene carbonate (EC) and Al₂SiO₅ in polymer host electrolytes has been investigated using FTIR ICP-OES spectrometry. Thermal studies of the systems have displayed a stable trend of glass temperature transition at elevated salt concentration whereas incorporation of EC and filler into the system results in the same pattern in their T_g values. Paper presented at the International Conference on Functional Materials and Devices 2005, Kuala Lumpur, Malaysia, June 6 – 8, 2005.