| 1. |
- Liang, D., et al.
(author)
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Structural, electronic, vibrational and optical properties of Bi-n clusters
- 2017
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In: Modern Physics Letters B. - : World Scientific Pub Co Pte Lt. - 0217-9849 .- 1793-6640. ; 31:28
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Journal article (peer-reviewed)abstract
- The neutral, anionic and cationic bismuth clusters with the size n up to 14 are investigated by using B3LYP functional within the regime of density functional theory and the LAN2DZ basis set. By analysis of the geometries of the Bin (n = 2-14)clusters, where cationic and anionic bismuth clusters are largely similar to those of neutral ones, a periodic effect by adding units with one to four atoms into smaller cluster to form larger cluster is drawn for the stable structures of bismuth clusters. An even odd alteration is shown for the properties of the clusters, such as the calculated binding energies and dissociation energies, as well as frontier orbital energies, electron affinities, ionization energies. All the properties indicate that the Bi-4 cluster is the most possible existence in bismuth-containing materials, which supports the most recent experiment. The orbital compositions, infrared and Raman activities and the ultraviolet absorption of the most possible tetramer bismuth cluster are given in detail to reveal the periodic tendency of adding bismuth atoms and the stability of tetramer bismuth cluster.
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| 2. |
- Tao, L. L., et al.
(author)
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Tension-induced mechanical properties of stanene
- 2016
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In: Modern Physics Letters B. - : World Scientific Pub Co Pte Lt. - 0217-9849 .- 1793-6640. ; 30:12, s. Art. no. 1650146-
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Journal article (peer-reviewed)abstract
- In this paper, elastic properties of stanene under equiaxial or uniaxial tensions along armchair and zigzag directions are investigated by first-principles calculations. The stress strain relation is calculated and the relaxation of the internal atom positions is analyzed. The high-order elastic constants are calculated by fitting the polynomial expressions. The Young's modulus and Poisson ratio of the stanene is calculated to be 24.14 N/m and 0.39 N/m, respectively. The stanene exhibits lower Young's modulus than those of the proceeding group IV elements, which is attributed to the smaller sp(2)-sp(3) bond energy in stanene than those of silicene and germanene. Calculated values of ultimate stresses and strains, second-order elastic constants (SOCEs) and the in-plane Young's modulus are all positive. It proves that stanene is mechanically stable.
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| 3. |
- Xu, H., et al.
(author)
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Raman spectroscopy of epitaxial topological insulator Bi2Te3 thin films on GaN substrates
- 2015
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In: Modern Physics Letters B. - : World Scientific Pub Co Pte Lt. - 0217-9849 .- 1793-6640. ; 29:15
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Journal article (peer-reviewed)abstract
- Bi2Te3 has drawn great attention in recent years as both a topological insulator and the best thermoelectric material at room temperature. We report on Raman spectroscopic study on Bi2Te3 thin films with thicknesses of 20-50 nm grown on GaN by molecular beam epitaxy. All the four classical optical phonon modes are clearly revealed for the first time in ex situ Raman for epitaxial Bi2Te3. Unusual and infrared-active vibration modes are also observed and analyzed. In the resonant Raman measurements, abnormal enhancement and suppression of different modes are studied. The interface modes caused by a large density of domain boundaries formed during coalescence of crystal islands with different lattice orientations and the Frohlich electron-phonon interaction are found to play significant roles during the Raman scattering processes.
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| 4. |
- Zhdanov, Vladimir, 1952
(author)
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A generic statistical model of hydride formation in a random alloy
- 2016
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In: Modern Physics Letters B. - : World Scientific Pub Co Pte Lt. - 0217-9849 .- 1793-6640. ; 30:26
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Journal article (peer-reviewed)abstract
- Hydride formation in metals (e.g. in Pd), accompanied by a hysteresis loop in the absorption isotherms, is one of the generic examples of first-order phase transitions (FOPTs). During the last decade, the corresponding experimental studies, driven by applications related to hydrogen storage, have shifted towards metal particles sized from a few nanometers to micrometers in general and to alloyed particles of these sizes in particular. The understanding of hydride formation in alloys is, however, still far from complete. Herein, a statistical model of hydride formation in a random alloy is presented. The model is focused on the situation when this process is favorable in metal 1 (e.g. Pd) and shows what may happen when atoms of metal 2 make it less favorable due to decrease of the hydrogen binding energy and/or attractive hydrogen hydrogen (H-H) interaction. Random distribution of metal atoms is taken explicitly into account. The attractive H-H interaction, including its dependence on fraction of metal 2 in the alloy, is described at the mean-field level. With increasing fraction of the latter metal, the critical temperature is found to decrease linearly or nonlinearly depending on the values of the model parameters. If the decrease of the hydrogen binding energy with increasing number of nearest-neighbor (nn) atoms of metal 2 is appreciable, the model predicts up to three hysteresis loops.
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| 5. |
- Firat, Coskun, et al.
(author)
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Characterization of density oscillations in confined and degenerate Fermi gases
- 2018
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In: Modern physics letters B. - 0217-9849. ; 32:32
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Journal article (peer-reviewed)abstract
- Friedel oscillations appear in density of Fermi gases due to Pauli exclusion principle and translational symmetry breaking nearby a defect or impurity. In confined Fermi gases, this symmetry breaking occurs also near to boundaries. Here, density oscillations of a degenerate and confined Fermi gas are considered and characterized. True nature of density oscillations are represented by analytical formulas for degenerate conditions. Analytical characterization is first done for completely degenerate case, then temperature effects are also incorporated with a finer approximation. Envelope functions defining the upper and lower bounds of these oscillations are determined. It is shown that the errors of obtained expressions are negligible as long as the system is degenerate. Numbers, amplitudes, averages and spatial coordinates of oscillations are also given by analytical expressions. The results may be helpful to efficiently predict and easily calculate the oscillations in density and density-dependent properties of confined electrons at nanoscale.
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| 6. |
- Wang, Kailin, et al.
(author)
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Electronic properties and band offsets in InP(1-x-y) BixNy
- 2019
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In: Modern Physics Letters B. - 0217-9849. ; 33:6
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Journal article (peer-reviewed)abstract
- Electronic band structures of InP(1-x-y)BixNy have been theoretically studied by using Conduction Band Anticrossing (CBAC) model and Valence Band Anticrossing model (VBAC) in conjugation with k . p method. This mathematical model's manifestation is a 16 band Hamiltonian matrix. Our results reveal that the addition of Bi and N to InP causes substantial reduction of band gap, and the conduction band offset is greater than valence band offset. It can provide better electronic confinement and improve the temperature-insensitive characteristics for optoelectronic devices. Material compositions and band gap under various strain conditions have also been added in our calculation. By adjusting the concentration of Bi and N, we obtained a strong control of conduction band edge and valence band edge, which increases the flexibility of design InPBiN/InP structures.
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| 7. |
- Zhang, Junyu, et al.
(author)
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K · p calculations of bismuth induced changes in band structure of InN1-XBix, GaN1-X Bix and AlN1-X Bix alloys
- 2018
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In: Modern Physics Letters B. - 0217-9849. ; 32:11
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Journal article (peer-reviewed)abstract
- Valence band anticrossing (VBAC) model is used to investigate band structure of InN1-xBix, GaN1-xBix and AlN1-xBix for the purpose of optimal performance group-III nitride related devices. Obvious reduction in band gap and increase in spin-orbit splitting energy are founded by doping dilute concentration of bismuth in all these III-N material. The band gap of GaN1-xBix and AlN1-xBix show a step change, and this can be explained by the special position relation between of Bi impurity energy level with corresponding host's band offsets. We also show how bismuth may be used to form alloys by finding the doping region ΔSO > Eg which can provide a means of suppressing non-radiative CHSH (hot-hole producing) Auger recombination and inter-valence band absorption. For InN1-xBix, bismuth concentration beyond 1.25% is found to be corresponding to the range of ΔSO > Eg and it shows a continuous adjustable band gap from 0.7 eV to zero. This may make InN1-xBix a potential candidate for near or mid-infrared optoelectronic applications.
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