250 research outputs found
Recent Advances in Novel Materials for Future Spintronics
As we all know, electrons carry both charge and spin. The processing of information in conventional electronic devices is based only on the charge of electrons. Spin electronics, or spintronics, uses the spin of electrons, as well as their charge, to process information. Metals, semiconductors, and insulators are the basic materials that constitute the components of electronic devices, and these types of materials have been transforming all aspects of society for over a century. In contrast, magnetic metals, half-metals (including zero-gap half-metals), magnetic semiconductors (including spin-gapless semiconductors), dilute magnetic semiconductors, and magnetic insulators are the materials that will form the basis for spintronic devices. This book aims to collect a range of papers on novel materials that have intriguing physical properties and numerous potential practical applications in spintronics
Optical properties of germanium dioxide in the rutile structure
Abstract.: We present first-principles calculations for the optical properties of germanium dioxide in the rutile structure. The electronic band structure has been calculated self-consistently within the local density approximation using the full-potential linearized augmented plane wave method. The electronic band structure shows that the fundamental energy gap is direct at the center of the Brillouin zone. The determinant role of a band structure computation with respect to the analysis of the optical properties is discusse
Optical properties of germanium dioxide in the rutile structure
We present first-principles calculations for the optical properties of germanium dioxide in the rutile structure. The electronic band structure has been calculated self-consistently within the local density approximation using the full-potential linearized augmented plane wave method. The electronic band structure shows that the fundamental energy gap is direct at the center of the Brillouin zone. The determinant role of a band structure computation with respect to the analysis of the optical properties is discussed
Structural, elastic, mechanical and thermodynamic properties of Terbium oxide: First-principles investigations
First-principles investigations of the Terbium oxide TbO are performed on structural, elastic, mechanical and thermodynamic properties. The investigations are accomplished by employing full potential augmented plane wave FP-LAPW method framed within density functional theory DFT as implemented in the WIEN2k package. The exchange-correlation energy functional, a part of the total energy functional, is treated through Perdew Burke Ernzerhof scheme of the Generalized Gradient Approximation PBEGGA. The calculations of the ground state structural parameters, like lattice constants a0, bulk moduli B and their pressure derivative BâČ values, are done for the rock-salt RS, zinc-blende ZB, cesium chloride CsCl, wurtzite WZ and nickel arsenide NiAs polymorphs of the TbO compound. The elastic constants (C11, C12, C13, C33, and C44) and mechanical properties (Young's modulus Y, Shear modulus S, Poisson's ratio Ï, Anisotropic ratio A and compressibility ÎČ), were also calculated to comprehend its potential for valuable applications. From our calculations, the RS phase of TbO compound was found strongest one mechanically amongst the studied cubic structures whereas from hexagonal phases, the NiAs type structure was found stronger than WZ phase of the TbO. To analyze the ductility of the different structures of the TbO, Pugh's rule (B/SH) and Cauchy pressure (C12âC44) approaches are used. It was found that ZB, CsCl and WZ type structures of the TbO were of ductile nature with the obvious dominance of the ionic bonding while RS and NiAs structures exhibited brittle nature with the covalent bonding dominance. Moreover, Debye temperature was calculated for both cubic and hexagonal structures of TbO in question by averaging the computed sound velocities
Ab-initio study of the stability and electronic properties of wurtzite and zinc-blende BeS nanowires
In this work we study the structural stability and electronic properties of
the Beryllium sulphide nanowires (NWs) in both zinc blende (ZB) and wurtzite
(WZ) phases with triangle and hexagonal cross section, using first principle
calculations within plane-wave pseudopotential method. A phenomenological model
is used to explain the role of dangling bonds in the stability of the NWs. In
contrast to the bulk phase, ZB-NWs with diameter less than 133.3 (angstrom) are
found to be less favorable over WZ-NWs, in which the surface dangling bonds
(DBs) on the NW facets play an important role to stabilize the NWs.
Furthermore, both ZB and WZ NWs are predicted to be semiconductor and the
values of the band gaps are dependent on the surface DBs as well as the size
and shape of NWs. Finally, we performed atom projected density-of states
(PDOSs) analysis by calculating the localized density of states on the surface
atoms, as well as on the core and edge atoms.Comment: 9 Pages, 6 Figure
Structural phase transition and opto-electronic properties of NaZnAs
In this study, we predict the structural phase transitions as well as opto-electronic properties of the filled-tetrahedral (Nowotny-Juza) NaZnAs compound. Calculations employ the full potential (FP) linearized augmented plane wave (LAPW) plus local orbitals (lo) scheme. The exchange-correlation potential is treated within the generalized gradient approximation of Perdew-Burke and Ernzerhof (GGA-PBE). In addition, Tran and Blaha (TB) modified Becke-Johnson (mBJ) potential is also used to obtain more accurate optoelectronic properties. Geometry optimization is performed to obtain reliable total energies and other structural parameters for each NaZnAs phase. In our study, the sequence of the structural phase transition on compression is Cu2Sb-type ? Ă ? a phase. NaZnAs is a direct (G-G) band gap semiconductor for all the structural phases. However, compared to PBE-GGA, the mBJ approximation reproduces better fundamental band gaps. Moreover, for insight into its potential for photovoltaic applications, different optical parameters are studied
HoloprosencĂ©phalie : A propos dâun cas
L'holoprosencĂ©phalie (HPE) est une malformation cĂ©rĂ©brale complexe rĂ©sultant d'une division incomplĂšte du prosencĂ©phale, survenant entre le 18Ăšme et le 28Ăšme jour de vie embryonnaire et affectant Ă la fois le cerveau et la face. Trois degrĂ©s de sĂ©vĂ©ritĂ© croissante ont Ă©tĂ© dĂ©crits : l'holoprosencĂ©phalie lobaire, semi-lobaire, et alobaire. Des anomalies de la face peuvent s'associer Ă la malformation cĂ©rĂ©brale (leur gravitĂ© reflĂšte grossiĂšrement le degrĂ© de sĂ©vĂ©ritĂ© de l'holoprosencĂ©phalie). Les Ă©tiologies sont essentiellement les anomalies chromosomiques et le diabĂšte maternel. Le diagnostic repose sur lâĂ©chographie et lâIRM antĂ©natales au troisiĂšme trimestre de la grossesse, la clinique, lâĂ©chographie trans-fontanellaire, la TDM et surtout lâIRM cĂ©rĂ©brale. Le diagnostic gĂ©nĂ©tique fait appel au caryotype. Nous dĂ©crivons un cas dâ holoprosencĂ©phalie dĂ©couverte aprĂšs un accouchement survenu Ă 30 SA, chez une patiente primigeste de 26 ans, mal suivie, ayant une consanguinitĂ© du premier degrĂ©, non supplĂ©mentĂ©e en acide folique, et ayant pris du fenugrec au cours du premier trimestre de sa grossesse. Dans la majoritĂ© des cas, le pronostic est rĂ©servĂ©. Â
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