Search results

1

2D B_xC_{1-x} Layers as Predicted by the Cluster-Expansion Approach

100%

Gonzalez Szwacki N.

|

vol. 126

|

issue 5

1215-1217

EN

In this work, the cluster-expansion method combined with extensive first-principles calculations is used for predicting the most stable 2D B_xC_{1-x} (x ≤0.5) layers. For concentrations of B up to ≈ 38%, the honeycomb structure of the boron-carbon compound is preserved, whereas for larger concentrations, the boron atoms tend to form 2D clusters and/or ribbons that are fragments of a triangular boron sheet. Our studies indicate that the incorporation of boron into graphene is energetically unfavorable even for low concentrations of B, however, the graphene-like structure of the B_xC_{1-x} layer may be stabilized by a metallic substrate.

2

Quantum Monte Carlo vs. Density Functional Methods for the Prediction of Relative Energies of Small Si-C Clusters

63%

Gonzalez Szwacki N., Majewski J.

Acta Physica Polonica A

|

2011

|

vol. 120

|

issue 5

964-966

EN

In the present paper, we assess the accuracy of popular and widely used approaches based on density functional theory by relating them to the most accurate at present quantum Monte Carlo calculations. As the test case, we consider the relative stability of small Si_{n}C_{m} isomers. We find out that none of the studied DFT approaches employing local, semilocal, or even hybrid functionals are able to predict correctly the relative stability of the isomers.

3

Structure and Energetics of Fragments of the Planar α and β Boron Sheets

51%

Gonzalez Szwacki N., Tarkowski T., Majewski J.

Acta Physica Polonica A

|

2016

|

vol. 129

|

issue 1a

A-148-A-149

EN

Large scale first principles calculations based on density functional theory and using hybrid exchange-correlation functionals have been performed in order to study the structural properties and the relative stability of fragments of the planar α and β boron sheets. Based on the considered structures, we show that, in contrast to the fragments of the α -sheet, all the fragments of the β -sheet, having more than ≈30 atoms, are fully planar regardless of their shape. We conclude that the β -sheet is the only planar boron sheet reported so far that retains planarity even if it is reduced to relatively small fragments.

4

Structural Properties of MnTe, ZnTe, and ZnMnTe

45%

Gonzalez Szwacki N., Przeździecka E., Dynowska E., Bogusławski P., Kossut J.

Acta Physica Polonica A

|

2004

|

vol. 106

|

issue 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.

5

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.

|

issue 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.

6

Elastic Properties of Zinc Blende MnTe

27%

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

|

vol. 106

|

issue 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.

Refine search results

6 Acta Physica Polonica A

1 2016

1 2014

1 2011

2 2004

1 2002

6 Gonzalez Szwacki N.

3 Bogusławski P.

2 Dynowska E.

2 Majewski J.

1 Christensen N.

1 Djemia P.

1 Gorczyca I.

1 Janik E.

1 Jouanne M.

1 Karczewski G.

1 Kossut J.

1 Kowalski B.

1 Morhange J.

1 Przeździecka E.

1 Roussigné Y.

1 Stashkevich A.

1 Svane A.

1 Szuszkiewicz W.

1 Tarkowski T.

2D B_xC_{1-x} Layers as Predicted by the Cluster-Expansion Approach

Quantum Monte Carlo vs. Density Functional Methods for the Prediction of Relative Energies of Small Si-C Clusters

Structure and Energetics of Fragments of the Planar α and β Boron Sheets

Structural Properties of MnTe, ZnTe, and ZnMnTe

Electronic Structure and Optical Properties of GaAs_{1-x}N_x and Ga_{1-x}B_xAs Alloys

Elastic Properties of Zinc Blende MnTe