Scattering and bound states of a nonrelativistic neutral spin-1/2 particle in a magnetic field

We have investigated the scattering and bound states of a nonrelativistic spin-1/2 particle in the system ofN magnetic barriers (or magnetic wells) andN magnetic delta functions. We have studied three types of problems: tunnelling with spin, band structure and change of polarization during transmission and reflection.     

Atomic and electronic structures and thermal stability of boron-nitrogen nanopeapods: B<Subscript>12</Subscript>N<Subscript>12</Subscript> fullerenes in BN nanotubes

The atomic structures, energies of formation, electronic structures, and thermal stabilities (in the temperature range T = 0–3000 K) of novel hybrid boron-nitrogen nanostructures (so-called nanopeapods B₁₂N₁₂@BN-NT) are simulated using the self-consistent density functional tight-binding (DFTB) method. The B₁₂N₁₂@BN-NT nanopeapods are regular linear ensembles of B₁₂N₁₂ boron-nitrogen fullerenes encapsulated in boron-nitrogen nanotubes (BN-NT), such as the (14, 0) nonchiral zigzag BN nanotubes, the (8, 8) nonchiral armchair BN nanotubes, and the (12, 4) chiral BN nanotubes.     

High frequency properties of a quasi-two-dimensional conductive film

The propagation of a monochromatic longitudinal acoustic wave along the low conductivity axis of a thin quasi-two-dimensional conductive film, in the absence of an external magnetic field, is studied theoretically. It is shown that under certain conditions the formation of both a standing ordinary wave (OAW) and an anomalous acoustic wave (AAW) is possible. The frequency dependence of the amplitudes of both waves is derived. For certain values of the characteristic parameters, the AAW in the film may be dominant. From the resonance conditions for the formation of standing OAW and AAW waves (especially the AAW), it is possible to obtain information about the electronic structure of the quasi-two-dimensional conductors, e.g. the corrugation parameter η or the relaxation properties of the charge carriers.     

Simulation of the structural,electronic, and magnetic properties of Fe<Subscript>3</Subscript>C<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>B<Subscript>x</Subscript> borocementites

The structural, electronic, and magnetic properties and the enthalpy of formation of iron borocementites Fe₃C_1?x B_x (x= 0, 0.25, 0.50, 0.75, 1.00) are analyzed using ab initio calculations in the framework of the electron density functional theory. It is found that the unit cell parameter a of the orthorhombic lattice increases linearly and the parameters b and c decrease as the boron concentration increases. The density of states at the Fermi level changes only slightly, and the main variations in the band structure occur in the region of the bottom of the valence bands. The magnetic moment of the iron atoms and the total magnetization and stability of the Fe₃C_1?x B_x phases increase linearly with an increase in the boron concentration.     

The dielectric model function. An evidence for the nu3(SO4-) phonon mixing in gypsum using polarized IR specular reflectance spectroscopy

A complete investigation of the phonon mixing in the nu3(SO4(2-)) frequency region was made, under experimental geometry where the reflecting crystal plane and the plane of incidence contain two principal dielectric axes. It was shown that although it is monoclinic, in the frequency region under inspection, gypsum could be treated as an orthorhombic crystal. More sophisticated model dielectric functions were introduced for the explanation of the Evans holes in the reflectance spectra. Using the model dielectric function, an appearance of the shoulder at the higher frequency part of the reflectance band was explained in terms of longitudinal and quasilongitudinal phonons. A possibility for Evans type interaction was encountered between the nu3(SO4(2-)) Au symmetry type mode and probably some of the combination modes.     

Band structure of new layered arsenides SrRu<Subscript>2</Subscript>As<Subscript>2</Subscript> and BaRu<Subscript>2</Subscript>As<Subscript>2</Subscript>

This paper reports on the results of the ab initio FLAPW-GGA band structure calculations for two new layered phases SrRu₂As₂ and BaRu₂As₂, which are isostructural and isoelectronic to the known tetragonal (Ca,Sr,Ba)Fe₂As₂ basis phases of the FeAs superconductor family. The energy bands, densities of states, topology of the Fermi surface, low-temperature electron specific heats, and molar Pauli paramagnetic susceptibilities of SrRu₂As₂ and BaRu₂As₂ are determined for the first time and discussed in comparison with those for BaFe₂As₂ and BaRh₂As₂.     

Splitting of Spectra in Anharmonic Oscillators Described by Kratzer Potential Function

A perturbation theory model that describes splitting of the spectra in highly symmetrical molecular species in electrostatic field is proposed. An anahrmonic model of a two-dimensional oscillator having Kratzer potential energy functionis used to model the molecular species and to represent the unperturbed system. A selection rule for the radial quantum number of the oscillator is derived. The eigenfunctions of a two-dimensional anharmonic oscillator in cylindrical coordinates are used for the matrix elements representing the probability for energy transitions in dipole approximation to be calculated. Several forms of perturbation operators are proposed to model the interactionbetween the polyatomic molecular species and an electrostatic field. It is found that the degeneracy is removed in the presence of the electric field and spectral splitting occurs. Anharmonic approximation for the unperturbed system is more accurate and reliable representation of a real polyatomic molecular species.     

Depicting the dehydration and dehydroxylation processes in very rare hydrogen arsenate minerals

Journal of Thermal Analysis and Calorimetry - The work represents a pioneering attempt to couple TG analysis and hot-stage t-ATR-FTIR spectroscopy to describe the dehydration and dehydroxylation...