| 1. |
- Liang, D., et al.
(författare)
-
Structural, electronic, vibrational and optical properties of Bi-n clusters
- 2017
-
Ingår i: Modern Physics Letters B. - : World Scientific Pub Co Pte Lt. - 0217-9849 .- 1793-6640. ; 31:28
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 2. |
- Lu, P. F., et al.
(författare)
-
Electronic and optical properties of InGaAs/GaAs quantum dots with tunable aspect-ratio
- 2014
-
Ingår i: Modern Physics Letters B. - : World Scientific Pub Co Pte Lt. - 0217-9849 .- 1793-6640. ; 28:9
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, a combined approach of finite element method (FEM) and quadratic programming optimization method is proposed to investigate the nonuniform equilibrium composition profile of InGaAs/GaAs quantum dots (QDs) in the framework of Gibbs energy optimization (GEO). The proposed QDs are varied with aspect ratio from 0.3 to 0.5. The wave functions of electron and heavy hole are predicted by using the k . p method. The changes of wave functions before and after optimization can be observed by using composition optimization. Both the eigenvalues and transition energy change obviously with the increasing aspect ratio. The linear optical absorption coefficients corresponding to the interband ground state transition are obtained via the density matrix approach and perturbation expansion method. The numerical results reveal that the aspect ratio and composition profile play significant roles in determining the electronic and optical properties.
|
|
| 3. |
- Nika, Grigor
(författare)
-
A gradient system for a higher-gradient generalization of Fourier’s law of heat conduction
- 2023
-
Ingår i: Modern physics letters B. - : World Scientific. - 0217-9849 .- 1793-6640. ; 37:11, s. 1-10
-
Tidskriftsartikel (refereegranskat)abstract
- We derive a generalized heat conduction problem for a rarefied gas at slip regime from a gradient system where the driving functional is the entropy. Specifically, we construct an Onsager system (X,S,Kheat) such that the associated evolution of the system is given by ∂tu=+Kheat(u)DS(u), where the Onsager operator, Kheat(u), contains higher-gradients of the absolute temperature u. Moreover, through Legendre-Fenchel theory we write the Onsager system as a classical gradient system (X,S,G) with an induced gradient flow equation, ∂tu=∇GDS(u). We demonstrate the usefulness of the approach by modeling scale-size thermal effects in periodic media that have been recently observed experimentally.
|
|
| 4. |
- Tao, L. L., et al.
(författare)
-
Tension-induced mechanical properties of stanene
- 2016
-
Ingår i: Modern Physics Letters B. - : World Scientific Pub Co Pte Lt. - 0217-9849 .- 1793-6640. ; 30:12, s. Art. no. 1650146-
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 5. |
- Xu, H., et al.
(författare)
-
Raman spectroscopy of epitaxial topological insulator Bi2Te3 thin films on GaN substrates
- 2015
-
Ingår i: Modern Physics Letters B. - : World Scientific Pub Co Pte Lt. - 0217-9849 .- 1793-6640. ; 29:15
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 6. |
- Zhang, X. L., et al.
(författare)
-
Structural and electronic properties of InPBi alloys
- 2014
-
Ingår i: Modern Physics Letters B. - : World Scientific Pub Co Pte Lt. - 0217-9849 .- 1793-6640. ; 28:17
-
Tidskriftsartikel (refereegranskat)abstract
- First-principle calculations have been performed to systematically investigate structural and electronic properties of InPBi alloys. The formation energy of seven different configurations is studied. The strength of covalent bonding largely depends on the strong s-p hybridization among In-5s, P-3p and Bi-6p states. The band gap of InPBi shrinks clearly with the increasing Bi concentration and the band edge shifts when spin-orbit coupling (SOC) is considered. The insertion of Bi atom leads to hybridization of In/P/Bi p states which contributes a lot around Fermi level. In addition, our results show that the biaxial strain is an effective method to tune the electronic properties of the system.
|
|
| 7. |
- Zhdanov, Vladimir, 1952
(författare)
-
A generic statistical model of hydride formation in a random alloy
- 2016
-
Ingår i: Modern Physics Letters B. - : World Scientific Pub Co Pte Lt. - 0217-9849 .- 1793-6640. ; 30:26
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 8. |
- Zhu, Xiaomei, et al.
(författare)
-
Friction on a Quantized Vortex in a Superfluid
- 1998
-
Ingår i: Modern physics letters B. - : World Scientific Pub Co Pte Lt. - 0217-9849 .- 1793-6640. ; 12:12, s. 451-458
-
Tidskriftsartikel (refereegranskat)abstract
- We obtain the explicit expression of the friction on a moving quantized vortex, following the formulation of Thouless, Ao and Niu. It is shown that the friction on a moving vortex is sensitive to details but does not change the transverse force. We provide a general thermodynamic interpretation for the mutual independence of the transverse force and the friction. The friction is evaluated for the case of quasiparticle contributions in a clean fermionic superfluid, showing a new feature of logarithmic divergence.
|
|
| 9. |
|
|
| 10. |
- Firat, Coskun, et al.
(författare)
-
Characterization of density oscillations in confined and degenerate Fermi gases
- 2018
-
Ingår i: Modern physics letters B. - 0217-9849. ; 32:32
-
Tidskriftsartikel (refereegranskat)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.
|
|
