| 1. |
- Adamczewski-Musch, J., et al.
(författare)
-
Production and electromagnetic decay of hyperons : a feasibility study with HADES as a phase-0 experiment at FAIR
- 2021
-
Ingår i: European Physical Journal A. - : Springer Nature. - 1434-6001 .- 1434-601X. ; 57:4
-
Tidskriftsartikel (refereegranskat)abstract
- A feasibility study has been performed in order to investigate the performance of the HADES detector to measure the electromagnetic decays of the hyperon resonances Sigma(1385)(0), Lambda(1405) and Lambda(1520) as well as the production of double strange baryon systems Xi(-) and Lambda Lambda in p + p reactions at a beam kinetic energy of 4.5GeV. The existing HADES detector will be upgraded by a new Forward Detector, which extends the detector acceptance into a range of polar angles that plays a crucial role for these investigations. The analysis of each channel is preceded by a consideration of the production cross-sections. Afterwards the expected signal count rates using a target consisting of either liquid hydrogen or polyethylene are summarized.
|
|
| 2. |
- Krivosheeva, A. V., et al.
(författare)
-
Band gap modifications of two-dimensional defected MoS2
- 2015
-
Ingår i: International Journal of Nanotechnology. - 1475-7435 .- 1741-8151. ; 12:8-9, s. 654-662
-
Tidskriftsartikel (refereegranskat)abstract
- The changes in structural and electronic properties, occurring in one monolayer of MoS2 at different concentrations of oxygen atoms doping and vacancies are investigated by means of ab initio computer simulation. The substitution of sulphur atoms by oxygen ones reduces the band gap for high concentrations only, transforming direct-gap semiconductor into an indirect one, whereas a smaller concentration of oxygen practically does not influence the gap. The presence of sulphur vacancies strongly reduces the band gap, leading to bands overlapping at high concentration and appearance of new bands at the gap region, which are determined by Mo 4d states with the mixture of S 3p states, at low concentrations.
|
|
| 3. |
- Kislinskiǐ, Yu V., et al.
(författare)
-
Copper oxide superconducting/antiferromagnetic interface
- 2015
-
Ingår i: Solid State Phenomena. - 1662-9779 .- 1012-0394. - 9783038354826 ; 233-234, s. 733-736
-
Konferensbidrag (refereegranskat)abstract
- Superconducting Nb/Au/Ca1-xSrxCuO2/YBa2Cu3O7 mesa-heterostructures were investigated. Dependencies of electrical parameters versus inverse capacitance were measured. A band diagram which takes into account an accumulation of holes inCa1-xSrxCuO2 interlayer and band bending due to difference of work functions was proposed. The dependencies of electrical parameters were analyzed by examining the quasipartical and superconducting currents.
|
|
| 4. |
- Migas, D. B., et al.
(författare)
-
Quasi-2D silicon structures based on ultrathin Me2Si (Me = Mg, Ca, Sr, Ba) films
- 2018
-
Ingår i: Surface Science. - : Elsevier B.V.. - 0039-6028 .- 1879-2758. ; 670, s. 51-57
-
Tidskriftsartikel (refereegranskat)abstract
- By means of ab initio calculations with hybrid functionals we show a possibility for quasi-2D silicon structures originated from semiconducting Mg2Si, Ca2Si, Sr2Si and Ba2Si silicides to exist. Such a 2D structure is similar to the one of transition metal chalcogenides where silicon atoms form a layer in between of metal atoms aligned in surface layers. These metal surface atoms act as pseudo passivation species stabilizing crystal structure and providing semiconducting properties. Considered 2D Mg2Si, Ca2Si, Sr2Si and Ba2Si have band gaps of 1.14 eV, 0.69 eV, 0.33 eV and 0.19 eV, respectively, while the former one is also characterized by a direct transition with appreciable oscillator strength. Electronic states of the surface atoms are found to suppress an influence of the quantum confinement on the band gaps. Additionally, we report Sr2Si bulk in the cubic structure to have a direct band gap of 0.85 eV as well as sizable oscillator strength of the first direct transition.
|
|
| 5. |
- Migas, D. B., et al.
(författare)
-
The Surface Energy and Band Structure of gamma-WO3 Thin Films
- 2017
-
Ingår i: Science of Advanced Materials. - : AMER SCIENTIFIC PUBLISHERS. - 1947-2935 .- 1947-2943. ; 9:3-4, s. 469-474
-
Tidskriftsartikel (refereegranskat)abstract
- By means of ab initio calculations we demonstrate sizable anisotropy in surface energy of the gamma-WO3 (001), (010) and (100) surfaces. The (001) surface has the smallest surface energy followed by the (010) and (100) surfaces. Their surface band structures are characterized by dispersion of bands near the gap region and by band-gap values similar to the ones of the bulk. The role of surface atoms in stabilizing the band gap is revealed. Variations in the position of the Fermi level are traced with respect to the different surface reconstructions.
|
|
| 6. |
- Migas, D. B., et al.
(författare)
-
Orientation effects in morphology and electronic properties of anatase TiO2 one-dimensional nanostructures. II. Nanotubes
- 2014
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 16:20, s. 9490-9498
-
Tidskriftsartikel (refereegranskat)abstract
- In the first part [D. B. Migas et al., Phys. Chem. Chem. Phys., 2014, DOI: 10.1039/C3CP54988G] by means of ab initio calculations we have analyzed and discussed anisotropy effects on electronic properties of 001 -, 100 - and 110 - oriented anatase TiO2 nanowires. In this part we present results indicating crucial changes in morphology of anatase TiO2 nanotubes originating from TiO2 nanowires by making a hole along the wire axis. The critical wall thickness has been found to exist for the nanotubes with 001 and 110 axes: at smaller thickness their shape can be rounded, squeezed, viewed as conglomerates of nanocrystals and even represented as cylindrical and `single-walled'- like structures formed without rolling up a thin titania layer into a nanotube. In general, band dispersion near the gap region of TiO2 nanotubes is close to the one of TiO2 nanowires with the same orientation. We have also revealed that optimization of the unit cell parameter along the wire axis and consideration of quantum confinement and surface state effects are important to provide an interpretation of band-gap variation with respect to wall thickness in TiO2 nanotubes.
|
|
| 7. |
- Alekseev, A. Yu, et al.
(författare)
-
Curvature-induced effects in semiconducting alkaline-earth metal silicide nanotubes
- 2021
-
Ingår i: Physica. E, Low-Dimensional systems and nanostructures. - : Elsevier BV. - 1386-9477 .- 1873-1759. ; 128
-
Tidskriftsartikel (refereegranskat)abstract
- By means of ab-initio techniques we have investigated changes in the structure and electronic properties of alkaline-earth metal silicide (Ca2Si, Mg2Si and MgCaSi) nanotubes caused by the curvature-induced effects. It is revealed that the curvature-induced effects can: 1) stabilize Mg2Si nanotubes in a phase, which is metastable for the parent 2D Mg2Si; 2) lead to an energy gain as a result of 2D to nanotube structural transformation in the case of ternary MgCaSi nanotubes; 3) modify the band dispersion and band gaps for nanotubes with the diameters less than 30 angstrom. In addition, Mg2Si and MgCaSi nanotubes are found to be direct band-gap (0.5-1.2 eV) materials with appreciable oscillator strength of the first direct transitions.
|
|
| 8. |
- Alekseev, A. Y., et al.
(författare)
-
Structural stability and electronic properties of 2D alkaline-earth metal silicides, germanides, and stannides
- 2020
-
Ingår i: Japanese Journal of Applied Physics. - : IOP PUBLISHING LTD. - 0021-4922 .- 1347-4065. ; 59
-
Forskningsöversikt (refereegranskat)abstract
- We present the results of an extended theoretical study of the structure, phonon, electronic and optical properties of 2D alkaline-earth metal silicides, germanides and stannides (2D Me2X, where Me=Mg, Ca, Sr, Ba and X=Si, Ge, Sn). The performed analysis has shown the occurrence of the pseudo passivation effect and ionic chemical bonding in these 2D Me2X. In addition, the preformed investigation of their phonon spectra has shown the absence of imaginary frequencies indicating the stability of these 2D structures. The band structure calculations performed using the hybrid functional have revealed that all 2D Me2X are semiconductors with the gap varying from 0.12 to 1.01 eV. Among them Mg- and Ca-based 2D materials are direct band-gap semiconductors with the first direct transition having appreciable oscillator strength. We also propose to consider ternary 2D silicides, germanides and stannides with different Me atoms as a feasible way to modify properties of parent 2D Me2X.
|
|
| 9. |
- Migas, D. B., et al.
(författare)
-
Effect of polaron formation on electronic, charge and magnetic properties of Nb12O29
- 2020
-
Ingår i: Journal of Alloys and Compounds. - : ELSEVIER SCIENCE SA. - 0925-8388 .- 1873-4669. ; 821
-
Tidskriftsartikel (refereegranskat)abstract
- We present the ab initio study of different phases of Nb12O29, which has been done in the framework of density functional theory using the onsite Hubbard-U correction applied to the Nb-d states. We vary the U parameter in between 0 and 7 eV and suggest U = 3.7-5.0 eV to be most appropriate for the description of Nb12O29. We show that one cannot get any adequate description of this oxide using the crystallographic unit cell but at least 3 times larger supercell is needed increased along the shortest lattice parameter b to accommodate lattice distortions associated with polaron formation. Our results obtained for the enlarged cells show the possibility of simultaneous co-existence of localized states (polaron formation) and delocalized states providing metal-like properties of Nb12O29, in qualitative agreement with available experimental data.
|
|
| 10. |
- Migas, Dmitri B., et al.
(författare)
-
Orientation effects in morphology and electronic properties of anatase TiO2 one-dimensional nanostructures. I. Nanowires
- 2014
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 16:20, s. 9479-9489
-
Tidskriftsartikel (refereegranskat)abstract
- By means of ab initio calculations we have revealed the existence of sizable anisotropy in electronic properties of anatase TiO2 nanowires with respect to orientation: nanowires with 001 , 100 and 110 axes are found to be direct band-gap, indirect band-gap and degenerate semiconductor materials, respectively. The degenerate semiconducting properties of 110 oriented TiO2 nanowires are predicted to be the intrinsic features closely connected with stoichiometry. A band-gap variation with nanowire diameter is also shown to display rather complex behavior characterized by a competition between quantum confinement and surface state effects that is fully compatible with the available contradictory experimental data. Finally, we propose a model to explain the band-gap variation with size in TiO2 nanowires, nanocrystals and thin films.
|
|
