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1
Content available remote Thermodynamic Stability of Two Rhombohedral Phases of Si_{0.5}Ge_{0.5} Alloy
100%
Bogusławski P.
Acta Physica Polonica A
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1991
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tom 80
|
nr 2
299-302
EN
Thermodynamic stability of two ordered phases, RS1 and RS2, of Si_{0.5}Ge_{0.5} alloy is considered. Bulk and surface formation enthalpies are calculated using the model Tersoff's potential. RS2 structure is unstable, but its (001) ordered surface is stable against segregation. Properties of RS1 are just the opposite.
2
Content available remote Surface Stability of Ordered Ga_{0.5}In_{0.5}P and GaAs_{0.5}Sb_{0.5} Alloys
100%
Bogusławski P.
Acta Physica Polonica A
|
1991
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tom 79
|
nr 1
125-128
EN
Formation enthalpies of (001) surfaces terminating ordered Ga_{0.5}In_{0.5}P and GaAs_{0.5}Sb_{0.5} alloys were calculated using the VFF model. For several ordered phases, chemically ordered surfaces were found to be stable against surface segregation. In particular, even phases unstable against bulk segregation may be terminated by a stable surface.
3
Content available remote Transition Metal Ions in Semiconductors: LDA, LDA+U, and Experiment
63%
Zakrzewski T. , Bogusławski P.
Acta Physica Polonica A
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2015
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tom 127
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nr 2
321-323
EN
Electronic structure of Cr, Mn, Fe, and Co transition metal (TM) ions in GaN and AlN was calculated within generalized gradient approximation and GGA+U. The +U term was considered as a free parameter with 0 < U < 5 eV. Comparison with available data for intracenter optical transitions for Fe and Mn shows that good agreement is obtained for values of U smaller than 1 eV.
4
Content available remote Magnetic Anisotropy in GeMnTe - ab initio Calculations
63%
Łusakowski A. , Bogusławski P.
Acta Physica Polonica A
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2014
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tom 126
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nr 5
1177-1179
EN
Density functional theory calculations of the energy of magnetic anisotropy in GeMnTe were performed using OpenMX package with fully relativistic pseudopotentials. The discussion of microscopic origin of magnetic anisotropy was conducted. The main conclusion is that the magnetic anisotropy is caused by interplaty between spin-orbit and Coulomb interactions. The discussion includes also the influence of the free carriers concentration on the amplitude of energy of magnetic anisotropy. The important role of the chemical disorder is also pointed out.
5
Content available remote Impact of Exchange-Correlations Effects (+U Corrections) on the Energy Levels of Mn and Fe Impurities in GaN and AlN: A Comparison with Experiment
63%
Zakrzewski T. , Bogusławski P.
Acta Physica Polonica A
|
2013
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tom 124
|
nr 5
898-900
EN
Electronic structure of Mn and Fe impurities in GaN and AlN are calculated within the density functional theory in the generalized gradient approximation without and with the +U corrections. The comparison with the available experimental data shows that the results obtained with U = 0 are in good agreement with experiment. Inclusion of +U corrections makes the agreement worse.
6
Content available remote Influence of Chemistry on the Energy Band Structure: AlAs Versus GaAs
63%
Bogusławski P. , Gorczyca I.
Acta Physica Polonica A
|
1991
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tom 80
|
nr 3
433-436
EN
Energy band structure of AlAs and GaAs is analyzed in terms of the energy structure of the constituent atoms. Conduction band wave functions are projected on s-, p-, and d-symmetry atomic orbitals. The resulting information is combined with the eigenenergies of Al and Ga atoms, in order to-discuss the character of the band gaps, and the sign of deformation potentials.
7
Content available Electronic Structure and Optical Properties of GaAs_{1-x}N_x and Ga_{1-x}B_xAs Alloys
45%
Gonzalez Szwacki N. , Bogusławski P. , Gorczyca I. , Christensen N. , Svane A.
Acta Physica Polonica A
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2002
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tom 102
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nr 4-5
633-641
EN
The electronic band structure of GaAs_{1-x}N_x (x=0.016 and 0.031) and Ga_{1-x}B_xAs (x= 0.031) is studied by ab initio calculations using a supercell approach. Based on ab initio calculations and group theory we present a comprehensive analysis of the electronic structure of GaAs:N and GaAs:B alloys. In particular, we study the effective mass of conduction electrons in GaAs:N as a function of pressure and the Fermi energy. We find that the lowest conduction band is strongly non-parabolic, which leads to an increase in the effective mass with the electron energy. The rate of the increase is enhanced by the hydrostatic pressure. Theoretical results are compared to experimental data, and a qualitative agreement is found.
8
Content available Structural Properties of MnTe, ZnTe, and ZnMnTe
45%
Gonzalez Szwacki N. , Przeździecka E. , Dynowska E. , Bogusławski P. , Kossut J.
Acta Physica Polonica A
|
2004
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tom 106
|
nr 2
233-238
EN
Structural properties of ZnTe, MnTe, and Mn_{1-x}Zn_xTe alloy with zinc-blende, NiAs, and wurtzite phases were investigated by ab initio calculations. The calculated structural properties are in good agreement with the available experimental data. Theory predicts that the zinc-blende phase is more stable than wurtzite for all compositions. Mn_{1-x}Zn_xTe samples with 0.01 < x < 0.20 were grown by MBE. X-ray analysis of their crystalline structure revealed the presence of zinc-blende, wurtzite, and NiAs phases. The dominant phase changes from NiAs for the sample with x=0.01 to wurtzite for x=0.20. The observed stabilization of the wurtzite phase is possibly due to the hexagonal structure of the MnTe buffer.
9
Content available Elastic Properties of Zinc Blende MnTe
26%
Djemia P. , Roussigné Y. , Stashkevich A. , Szuszkiewicz W. , Gonzalez Szwacki N. , Dynowska E. , Janik E. , Kowalski B. , Karczewski G. , Bogusławski P. , Jouanne M. , Morhange J.
Acta Physica Polonica A
|
2004
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tom 106
|
nr 2
239-247
EN
The Brillouin light scattering was used to investigate elastic properties of the zinc blende, MBE-grown MnTe layer that was deposited on a (001) GaAs substrate covered by CdTe buffer layer. The three elastic constants of the zinc blende MnTe, namely c_{11}, c_{12}, and c_{44}, were directly determined for the first time from the frequency of the Rayleigh mode, of the pseudo-surface mode, and of the shear horizontal bulk mode traveling parallel to the layer surface. The value of c_{11} was checked using the frequency of longitudinal bulk waves propagating at different angles from the normal of the layer plane. This value was also independently determined by results of the folding of acoustic phonons, observed for MnTe/CdTe superlattices by the Raman scattering. Finally, the bulk modulus given by the formula B=(c_{11}+2c_{12})/3 was determined for zinc blende MnTe by ab initio calculations making use of the density functional theory and atomic pseudopotentials; spin polarization of MnTe was taken into account. A satisfactory agreement between theoretical and experimental values was obtained.
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