scholarly journals Possible superconductivity in Bismuth (111) bilayers. Their electronic and vibrational properties from first principles

MRS Advances ◽  
2018 ◽  
Vol 3 (6-7) ◽  
pp. 313-319 ◽  
Author(s):  
David Hinojosa-Romero ◽  
Isaías Rodriguez ◽  
Alexander Valladares ◽  
Renela M. Valladares ◽  
Ariel A. Valladares
Keyword(s):  
Density Of States ◽  
First Principles ◽  
Periodic Boundary ◽  
Periodic Boundary Conditions ◽  
Vibrational Properties ◽  
Superconducting Transition ◽  
Electronic Density ◽  
Densities Of States ◽  
Pairing Potential ◽  
Vibrational Density

ABSTRACTUsing a 72-atom supercell we report ab initio calculations of the electronic and vibrational densities of states for the bismuth (111) bilayers (bismuthene) with periodic boundary conditions and a vacuum of 5 Å, 10 Å and 20 Å. We find that the electronic density of states shows a metallic character at the Fermi level and that the vibrational density of states manifests the expected gap due to the layers. Our results indicate that a vacuum down to 5 Å does not affect the electronic and vibrational structures noticeably. A comparison of present results with those obtained for the Wyckoff structure is displayed. Assuming that the Cooper pairing potential is similar for all phases and structures of bismuth, an estimate of the superconducting transition temperature gives 2.61 K for the bismuth bilayers.

Doping site identification in 112 iron pnictides through a first-principles core-electron spectroscopic study

2019 ◽  
Vol 26 (4) ◽  
pp. 1367-1373 ◽  
Author(s):  
Haranath Ghosh ◽  
Soumyadeep Ghosh ◽  
Abyay Ghosh
Keyword(s):  
Absorption Spectra ◽  
Density Of States ◽  
First Principles ◽  
Density Functional ◽  
Chain Structure ◽  
Zigzag Chain ◽  
Superconducting Transition ◽  
Core Electron ◽  
Edge Absorption ◽  
Site Identification

Density functional theory based first-principles core-electron spectroscopic studies on iron-based superconducting 112 materials are presented. The existence of an extra As zigzag chain structure along with Fe–As planes in 112 materials is emphasised. Doping on an As site belonging to a chain by Sb is found to enhance the superconducting transition temperature. This is also shown from calculations with enhanced density of states when doped on chain-As. Therefore, As site identification in 112 is crucial. Theoretically computed As K-edge absorption spectra of two different types of As atoms for Ca0.85La0.15FeAs2 show a distinctly different nature. The sensitivities of As K-edge absorption spectra in the presence and absence of the `core-hole effect' are presented for future possible identification of the same experimentally. In both cases absorption spectra contain several features, the origins of which are thoroughly described in terms of site projected density of states results.

Vibrational Properties of Si Microclusters and Comparison to the Amorphous Material

1990 ◽  
Vol 206 ◽  
Author(s):  
Joseph L. Feldman ◽  
Efthimios Kaxiras
Keyword(s):  
Density Of States ◽  
Interatomic Potential ◽  
Amorphous Material ◽  
Vibrational Properties ◽  
Dynamical Matrix ◽  
Vibrational Density Of States ◽  
Remarkable Similarity ◽  
Surface Reconstructions ◽  
Amorphous Si ◽  
Vibrational Density

ABSTRACTThe lattice vibrational properties of two clusters of Si atoms are studied using the Stillinger-Weber phenomenological interatomic potential to calculate the dynamical matrix. The clusters contain 33 and 45 atoms, and their structure was postulated from considerations of surface reconstructions in analogy to crystalline Si surfaces. A remarkable similarity to the vibrational density of states of amorphous Si is demonstrated especially for the 45 atom cluster.

Structural phase transition, electronic, elastic, and vibrational properties of LiAl intermetallic compound: insights from first-principles calculations

2017 ◽  
Vol 95 (8) ◽  
pp. 691-698
Author(s):  
Y. Mogulkoc ◽  
Y.O. Ciftci ◽  
G. Surucu
Keyword(s):  
Phase Transition ◽  
Density Of States ◽  
Structural Phase Transition ◽  
First Principles ◽  
Density Functional ◽  
Structural Phase ◽  
Type Structure ◽  
Vibrational Properties ◽  
First Principles Calculations ◽  
Electronic Band

Using the first-principles calculations based on density functional theory (DFT), the structural, elastic, electronic, and vibrational properties of LiAl have been explored within the generalized gradient approximation (GGA) using the Vienna ab initio simulation package (VASP). The results demonstrate that LiAl compound is stable in the NaTl-type structure (B32) at ambient pressure, which is in good agreement with the experimental results and there is a structural phase transition from NaTl-type structure (B32) to CsCl-type structure (B2) at around 22.2 GPa pressure value. The pressure effects on the elastic properties have been discussed and the elastic property calculation indicates that the elastic instability could provide a phase transition driving force according to the variations relation of the elastic constant versus pressure. To gain further information about this, we also have investigated the other elastic parameters (i.e., Zener anisotropy factor, Poisson’s ratio, Young’s modulus, and isotropic shear modulus). The electronic band structure, total and partial density of states, phonon dispersion curves, and one-phonon density of states of B2 and B32 phases are also presented with results.

The Study of Electronic Density of States and Optical Properties of ZnO Nanotube by First-Principles

2015 ◽  
Vol 713-715 ◽  
pp. 2966-2969
Author(s):  
Yue Fan ◽  
Shao Chang Chen
Keyword(s):  
Optical Properties ◽  
Fermi Level ◽  
Density Of States ◽  
First Principles ◽  
Electronic Density ◽  
Electronic Density Of States ◽  
Zno Nanotube ◽  
Narrow Energy Range ◽  
Wide Energy ◽  
Better Than

In this paper, we studied the electronic density of states (DOS) and optical properties ZnO using first-principles method. We find that the electronic density of states was different in bulk ZnO and ZnO nanotube. The DOS of bulk ZnO spread at wide energy while the DOS of ZnO nanotube concentrated in a narrow energy range. The peak around-18 eV moved to a higher energy. The peaks more than Fermi level concentrated to the Fermi level, which meant the conductivity of ZnO nanotube was better than that of bulk ZnO. We also calculated the optical properties of ZnO nanotube. The optical properties showed that there were peaks around 8 eV, which may come from electrons transition between Zn 3dand O 2pstates. Our calculation provided a reference for the application of ZnO nanotube in optical devices.

Ab initio study of hydrogen chemisorption in nitrogen-doped carbon nanotubes

2016 ◽  
Vol 18 (36) ◽  
pp. 25663-25670 ◽  
Author(s):  
Julian David Correa ◽  
Elizabeth Florez ◽  
Miguel Eduardo Mora-Ramos
Keyword(s):  
Carbon Nanotubes ◽  
First Principles ◽  
Density Functional ◽  
Periodic Boundary ◽  
Periodic Boundary Conditions ◽  
Hydrogen Chemisorption ◽  
Ab Initio Study ◽  
Functional Theory ◽  
Nitrogen Doped ◽  
Nitrogen Doped Carbon

The electronic structure of single walled nitrogen-doped carbon nanotubes is calculated by first principles using density functional theory within the supercell approach with periodic boundary conditions.

Vibrational Properties of Silver Nanoparticles and Nanocrystalline Materials

2000 ◽  
Vol 634 ◽  
Author(s):  
Ralf Meyer
Keyword(s):  
Density Of States ◽  
Nanocrystalline Materials ◽  
Nanocrystalline Material ◽  
Vibrational Properties ◽  
Pressureless Sintering ◽  
Silver Particles ◽  
Vibrational Density Of States ◽  
Cluster A ◽  
Dynamics Simulations ◽  
Vibrational Density

ABSTRACTThe vibrational density of states of silver in the form of a free cluster, a single crystal and a nanocrystalline material has been calculated with the help of molecular-dynamics simulations. The model for the nanocrystalline material was derived by the simulation of pressureless sintering of nanometer sized silver particles. The results show a broadening of the vibrational density of states in the case of the cluster and the nanocrystalline material.

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