Full-text resources of PSJD and other databases are now available in the new Library of Science.
Visit https://bibliotekanauki.pl
Preferences help
Polish version English version Language
enabled [disable] Abstract
Number of results

Results found: 12

Number of results on page
first rewind previous Page / 1 next fast forward last

Search results

Search:
in the keywords:  61.72.Bb
help Sort By:

help Limit search:
first rewind previous Page / 1 next fast forward last
1
Content available remote

Calculation of Lattice Relaxation in Some Substitutional Alloys Using a Green Function

100%
Das S., Datta Roy (Paul) S.
|
|
vol. 95
|
issue 3
359-366
EN
In this paper we calculate nearest neighbour relaxation in some dilute substitutional alloys using a lattice static Green function and the Morse potential function. Distant neighbour relaxation is calculated by invoking a continuum approximation. The potential parameters for the unlike interactions are calculated using simple interpolation formulae. Using the above relaxation, we calculate volume changes in the above alloys. It is observed that the simple model predicts values which are in reasonably good agreement with the experimental values in all cases. The calculated values are also compared with those obtained from the Vegard law. For Au-Ag alloy, our model reproduces both the correct sign and the magnitude of the volume change, whereas the Vegard law cannot even give the sign of the volume change. This shows the inherent strength of the present model.
2
Content available remote

A Green Function Estimation of Correction to Vegard's Law for isovalent Substitutional Defects in Alkali Halide Crystals

100%
Datta Roy (Paul) S., Das S.
Acta Physica Polonica A
|
2000
|
vol. 97
|
issue 4
671-679
EN
A Green function method is developed for estimation of lattice parameter r(χ) of an AX-BX solid solution over entire composition range (χ=0 to 1). The r(χ) obtained in the present method is different from the value r_{V}(χ) suggested by Vegard's law. We estimated the deviation from Vegard's law, r(χ)-r_{V}(χ), over entire composition range for isovalent substitutional defect in alkali halide crystals. When compared to X-ray diffraction measurements, we find that the deviation is in correct direction, variation of r(χ) with χ is consistent with experiment and the overall agreement is fairly good considering the accuracy of the experiment.
3
Content available remote

Theoretical Studies of ESR Parameters and Local Lattice Structure of the Vanadate-Lithium-Borate Glasses

80%
Feng W., Zhao M., Li T., Zhang X., Xue J.
Acta Physica Polonica A
|
2012
|
vol. 122
|
issue 1
167-169
EN
Electron spin resonance spectral parameters of V^{4+} ions in vanadate-lithium-borate glasses have been calculated by the crystal-field theory. The theoretical results are g_{∥ } = 1.940, g_{⊥} = 1.983 and A_{∥ } = -175×10^{-4} cm^{-1}, A_{⊥} = -65×10^{-4} cm^{-1} which are good agreement with the experimental values (g_{∥ } = 1.939(3), g_{⊥} = 1.998(3) and A_{∥ } = (170.6-176.4)×10^{-4} cm^{-1}, A_{⊥} = (61.3-71.4)×10^{-4} cm^{-1}). In addition, the bond lengths of the local lattice structure are, respectively, R_{∥ } = 1.5 Å and R_{⊥} = 1.95 Å which have been shown to have a compressed tetrahedral geometry along the C_4 axis.
4
Content available remote

Phase Field Modeling of the Zn_{1-x}Cd_xO Solid Solutions

80%
Shtepliuk I., Podolskaia N., Lashkarev G.
|
|
vol. 126
|
issue 5
1079-1082
EN
The analysis of spinodal decomposition in the Zn_{1-x}Cd_xO ternary alloy was carried out by means of the nonlinear Cahn-Hilliard equation. Interaction parameter as a function of composition x was provided by valence force field simulations and was used in this analysis. The morphological patterns for the ternary alloys with different Cd content (x=5, 10, 50%) were experimentally obtained using the semi-implicit Fourier-spectral method. The simulated microstructure evolution Zn_{0.95}Cd_{0.05}O demonstrates that the microstructure having a form of bicontinuous worm-like network is evolved with the progress of aging. An effect of the phase-field mobility and the gradient energy on the microstructure evolution of the Zn_{1-x}Cd_xO alloys is discussed. It was found that the higher driving force for the decomposition in the higher Cd content film results in a higher decomposition rate revealed by the simulations. The temporal evolution of the simulated Zn_{0.95}Cd_{0.05}O microstructure is in good agreement with experimental results, which have been obtained for this solid solution.
5
Content available remote

Evolution of Matrix-Twin Interfaces of (101̅2) Twin in Magnesium

80%
Ostapovets A., Serra A.
Acta Physica Polonica A
|
2015
|
vol. 128
|
issue 4
661-663
EN
Recently, the presence of basal-prismatic interfaces in hexagonal close packed metals became subject of intensive investigation. We model the {101̅2} twin in magnesium bounded by two types of boundaries, i.e. {101̅2} interface and basal-prismatic facets. The migration of all boundary types is mediated by the motion of interfacial disconnections. It was shown that basal-prismatic interfaces play an important role in twin growth. The lengths of basal-prismatic facets remain constant during migration independently of the applied strain. In contrast, the {101̅2} interfaces increase their lengths during growth.
6
Content available remote

Defects and Defect Reactions in Semiconductor Nitrides

80%
Van de Walle C., Neugebauer J., Stampfl C., McCluskey M., Johnson N.
|
|
vol. 96
|
issue 5
613-627
EN
We report a comprehensive investigation of native point defects and impurities in GaN, AlN, and AlGaN alloys, with the goal of understanding doping limitations in nitride semiconductors. Unintentional incorporation of impurities (mainly oxygen) explains the tendency of nitride semiconductors to exhibit n-type conductivity. Silicon is the n-type dopant of choice; it remains shallow in AlGaN up to high Al content, while oxygen undergoes a DX transition. Experimental evidence for DX centers will be discussed. In p-type material, Mg doping is hindered by an increase in ionization energy with increasing Al content in AlGaN, and by nitrogen vacancies acting as compensating centers. Complex formation between magnesium and oxygen and between magnesium and nitrogen vacancies will be discussed.
7
Content available remote

Paramagnetic State of Hydrogen-Passivated Double-Donor Centers in Silicon

80%
Gregorkiewicz T., Zevenbergen I., Martynov Y., Ammerlaan C.
Acta Physica Polonica A
|
1995
|
vol. 88
|
issue 4
735-738
EN
Hydrogenation of two double donor centers in silicon - substitutional sulfur and thermal donor - is studied by electron paramagnetic resonance and electron-nuclear double resonance. For both centers the existence of a new paramagnetic S = 1/2 state identified as the neutral charge state of the double donor passivated with a single hydrogen atom is concluded. The microscopic structure of such complexes is discussed.
8
Content available remote

Mould Walls Inclination and Dendritic Morphology of CMSX-4 Blades Airfoils

80%
Krawczyk J., Bogdanowicz W., Sieniawski J., Kubiak K.
|
EN
The airfoils of single-crystalline turbine blades were studied. The blades made of industrial CMSX-4 superalloy were obtained by the Bridgman technique. Five different withdrawal rates (1-5 mm/min) were used. Series of as-cast samples were prepared by cutting the airfoils at different distances from the blade root. The metallographic sections, prepared for each cutting planes, were subjected to scanning electron microscopy observations and Laue diffraction studies. Macrostructure images of whole area of airfoil cross-sections were obtained by stitching several obtained SEM images. Morphology of dendrites in different area of cross-sections were analysed. The crystal orientation of each sample were determined by analysis of Laue pattern. It was found that the morphology of dendrites changes in the area, where the dendrite growth is limited by inclined mould walls.
9
Content available remote

Explanation of the Optical Spectra and Spin-Hamiltonian Parameters for Nickel(II) in Cadmium Bromide Crystal

80%
Gong J., Wang L., Feng W., Yang X., Zhang F.
Acta Physica Polonica A
|
2011
|
vol. 120
|
issue 3
497-500
EN
Based on crystal- and ligand-field theory, double-spin-orbital coupling approach was used to analyze the crystal-field energy levels and spin-Hamiltonian parameters of Ni^{2+} ion at trigonal site in CdBr_2. The local lattice distortion (Δ R and τ_{Ni^{2+}}) is estimated from the crystal field parameters; the crystal field energy Hamiltonian was diagonalized in the full basis consisting of 45 wave functions of the Ni^{2+} ion. Results of calculations are in good agreement with experimental data. The reasonableness of the theoretical results is discussed.
10
Content available remote

Investigations of the Optical Band Positions and Spin-Hamiltonian Parameters for the Rhombic VO^{2+} Complex in CsCl Crystal

80%
Fang W., Zheng W., Yang D., Tang H.
|
|
vol. 125
|
issue 5
1206-1209
EN
The optical band positions and spin-Hamiltonian parameters (g factors g_{i} and hyperfine structure constants A_{i}, where i=x, y, z) of the rhombic VO^{2+} complex in CsCl crystal are calculated together from two theoretical methods. One is the complete diagonalization (of energy matrix) method and another is the perturbation theory method. The calculated results from the two methods coincide and are in reasonable agreement with the experimental values. So, both methods are effective in the explanations of optical and electron paramagnetic resonance (EPR) data for d^1 ions in crystals. The calculations also suggest that in d^1 rhombic octahedra the ground state is almost a pure | d_{xy} ⟩ state. This point is different from that of conjugate d^9 (e.g., Cu^{2+}) ions in rhombic octahedra where the ground state should be an admixture of ground and first excited states.
11
Content available remote

Theoretical Explanations of the Optical Band Positions and Local Structure for Cu^{2+} Centers in ZnO-Bi_{2}O_{3}-B_{2}O_{3}-CuO Glasses

80%
Yuan M.
|
|
vol. 126
|
issue 6
1293-1295
EN
The local structure, two optical band positions and three electronic spin resonance parameters for Cu^{2+} centers at the tetragonally-distorted octahedral sites in ZnO-Bi_2O_3-B_2O_3-CuO glasses are calculated from the high-order perturbation method based on the two-spin-orbit-parameter model, where the contributions from both the spin-orbit coupling parameters of central d^{n} ion and ligand ion are included. The theoretical results are in good agreement with the experimental values. The calculations show that the high-order perturbation method based on the two-spin-orbit-parameter model is effective in the explanations of optical spectra, electronic spin resonance parameters and local distortion structure for d^{9} ions in glasses.
12
Content available remote

An ab initio Study of a Model of Single Wall GaN Nanotubes with Oxygen and Zinc as Impurities: Structural and Electronic Properties

80%
Rezouali K., Belkhir M.
Acta Physica Polonica A
|
2008
|
vol. 113
|
issue 2
713-722
EN
We report a comprehensive theoretical study of structural and electronic properties of substitutional oxygen and zinc contaminations in a model of single wall GaN nanotubes by means of ab initio supercell calculations. Our investigation yields many interesting results. The following ones deserve to be developed. Oxygen forms a shallow donor in the single wall GaN nanotubes as in bulk GaN polytypes. Its ionization energy is deeper than its counterpart in the bulk wurtzite GaN, so it can be a suitable n-type dopant in high temperature applications. Zinc is a relatively shallow acceptor at gallium site. It behaves as charge carrier trap at nitrogen site. The site preference of zinc impurity depends on the stoichiometry. Zinc at gallium site has small ionization energy, thus it would be an efficient p-dopant in GaN nanotubes unlike in bulk GaN polytypes.
first rewind previous Page / 1 next fast forward last
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.