scholarly journals Ab Initio Calculation of Li-Sn System: Unraveling New Phases of Superconducting Materials with Increasing Compression

2021 ◽  
Vol 1 (1) ◽  
pp. 1-15
Author(s):  
Thong Leng Lim ◽  
Tiem Leong Yoon ◽  
Yee Hui Robin Chang ◽  
San Kiong Lai
Keyword(s):  
Density Functional ◽  
Mechanical Stability ◽  
Careful Examination ◽  
Moderate Pressure ◽  
High Electron ◽  
Superconducting Transition ◽  
Energy Bands ◽  
Intermediate Phases ◽  
High Electron Concentration ◽  
Genetic Algorithm Approach

Stoichiometry, crystal compound, electronic attributes and superconductivity of compressed lithium-tin composites have been thoroughly studied using quantum mechanical genetic algorithm approach and the first principles computations based on density functional theory. Our simulations at moderate pressure (5-20 GPa) predict a complex convex hull diagram, with the following stable Li‑rich phases: I4/mmm-Li6Sn2, -Li7Sn2, -Li5Sn2, Ama2-Li4Sn2, -Li5Sn2, -Li6Sn2, C2/m-Li4Sn1, P21/m-Li6Sn2, -Li7Sn2 and Cmcm-Li4Sn2. Careful examination at their independent elastic parameters reveals sufficient mechanical stability in them. These phases are metallic system, with reasonably high electron concentration near to Fermi level or N(EF) that ranges from 0.6 to 2.4 states/eV cell. It is also interesting for us to observe soft modes and steep-flat energy bands at Fermi levels of Li6Sn2 structures which are stable throughout the pressure range. These features are prerequisites for superconducting behavior. Linear response function with Gaussian and tetrahedron methods reveals satisfactory superconducting transition temperature Tc (3.1 ~ 6.6 K) and Tc (2.1 ~ 2.4 K), respectively. Structural transition results for based elements Li and Sn agree well with literature thus signifying reliable prediction of intermediate phases.

scholarly journals The effect of pressure and alloying on half-metallicity of quaternary Heusler compounds CoMnYZ (Z = Al, Ga, and In)

2016 ◽  
Vol 34 (4) ◽  
pp. 905-915 ◽  
Author(s):  
M. Rahmoune ◽  
A. Chahed ◽  
A. Amar ◽  
H. Rozale ◽  
A. Lakdja ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Density Functional ◽  
Heusler Alloys ◽  
Band Gaps ◽  
Ferromagnetic Behavior ◽  
Full Potential ◽  
Energy Bands ◽  
Half Metallicity ◽  
Half Metallic ◽  
Electronic And Magnetic Properties

AbstractIn this work, first-principles calculations of the structural, electronic and magnetic properties of Heusler alloys CoMnYAl, CoMnYGa and CoMnYIn are presented. The full potential linearized augmented plane waves (FP-LAPW) method based on the density functional theory (DFT) has been applied. The structural results showed that CoMnYZ (Z = Al, Ga, In) compounds in the stable structure of type 1+FM were true half-metallic (HM) ferromagnets. The minority (half-metallic) band gaps were found to be 0.51 (0.158), 0.59 (0.294), and 0.54 (0.195) eV for Z = Al, Ga, and In, respectively. The characteristics of energy bands and origin of minority band gaps were also studied. In addition, the effect of volumetric and tetragonal strain on HM character was studied. We also investigated the structural, electronic and magnetic properties of the doped Heusler alloys CoMnYGa1−xAlx, CoMnYAl1−xInx and CoMnYGa1−xInx (x = 0, 0.25, 0.5, 0.75, 1). The composition dependence of the lattice parameters obeys Vegard’s law. All alloy compositions exhibit HM ferromagnetic behavior with a high Curie temperature (TC).

Theoretical Investigations on Mechanical Stability and Electronic Structure of NbN under Pressures

2011 ◽  
Vol 90-93 ◽  
pp. 1264-1271
Author(s):  
Xiao Feng Li ◽  
Jun Yi Du
Keyword(s):  
Debye Temperature ◽  
Density Functional ◽  
Mechanical Stability ◽  
Structural Parameters ◽  
Theoretical Data ◽  
Hexagonal Structure ◽  
Functional Theory ◽  
Theoretical Investigations ◽  
Crystallographic Structures ◽  
Good Agreement

The ground structure, elastic and electronic properties of several phases of NbN are determined based on ab initio total-energy calculations within the framework of density functional theory. Among the five crystallographic structures that have been investigated, the hexagonal phases have been found to be more stable than the cubic ones. The calculated equilibrium structural parameters are in good agreement with the available experimental results. The elastic constants of five structures in NbN are calculated, which are in consistent with the obtained theoretical and experimental data. The corresponding Debye temperature and elastic ansitropies are also obtained. The Debye temperature of NbN in various structures consistent with available experimental and theoretical data, in which the Debye temperature of δ-NbN is highest. The anisotropies of ZB-NbN, NaCl-NbN, CsCl-NbN gradually increases. For hexagonal structure, the anisotropies of ε-NbN are stronger than that of δ-NbN. The electronic structures of NbN under pressure are investigated. It is found that NbN have metallization and the hybridizations of atoms in NbN under pressure become stronger.

scholarly journals Mechanical properties of zirconium alloys and zirconium hydrides predicted from density functional perturbation theory

2015 ◽  
Vol 44 (43) ◽  
pp. 18769-18779 ◽  
Author(s):  
Philippe F. Weck ◽  
Eunja Kim ◽  
Veena Tikare ◽  
John A. Mitchell
Keyword(s):  
Mechanical Properties ◽  
Perturbation Theory ◽  
Elastic Properties ◽  
Density Functional ◽  
Mechanical Stability ◽  
Zirconium Alloys ◽  
Density Functional Perturbation Theory ◽  
Zirconium Hydrides

The elastic properties and mechanical stability of zirconium alloys and zirconium hydrides have been investigated within the framework of density functional perturbation theory. Results show that the lowest-energy Pn3̄m δ-ZrH1.5 phase is not mechanically stable.

scholarly journals Pressure Effect on Elastic Constants and Related Properties of Ti3Al Intermetallic Compound: A First-Principles Study

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2015 ◽  
Author(s):  
Xianshi Zeng ◽  
Rufang Peng ◽  
Yanlin Yu ◽  
Zuofu Hu ◽  
Yufeng Wen ◽  
...  
Keyword(s):  
Intermetallic Compound ◽  
Debye Temperature ◽  
Elastic Constants ◽  
First Principles ◽  
Density Functional ◽  
Mechanical Stability ◽  
Theoretical Data ◽  
Young’S Moduli ◽  
Anisotropic Factor ◽  
Isotropic Pressure

Using first-principles calculations based on density functional theory, the elastic constants and some of the related physical quantities, such as the bulk, shear, and Young’s moduli, Poisson’s ratio, anisotropic factor, acoustic velocity, minimum thermal conductivity, and Debye temperature, are reported in this paper for the hexagonal intermetallic compound Ti 3 Al. The obtained results are well consistent with the available experimental and theoretical data. The effect of pressure on all studied parameters was investigated. By the mechanical stability criteria under isotropic pressure, it is predicted that the compound is mechanically unstable at pressures above 71.4 GPa. Its ductility, anisotropy, and Debye temperature are enhanced with pressure.

scholarly journals Properties of InGaN deposited on Glass at Low Temperature

1997 ◽  
Vol 2 ◽  
Author(s):  
Tilman Beierlein ◽  
S. Strite ◽  
A. Dommann ◽  
D. J. Smith
Keyword(s):  
Low Temperature ◽  
Indium Tin Oxide ◽  
High Electron ◽  
Transparent Conductor ◽  
High Background ◽  
X Ray ◽  
Substrate Heating ◽  
Glass Substrates ◽  
High Electron Concentration ◽  
Background Absorption

We have investigated the properties of InGaN grown at low temperature on glass substrates by a plasma enhanced MBE process. The goal of this study was to evaluate the potential of InGaN as an oxide-free, transparent conductor material which could be deposited at or slightly above room temperature with minimal interaction or damage to the underlying material. InxGa1−xN films deposited on glass, even without substrate heating, are highly crystalline, but the crystallinity as measured by x-ray degrades at x < 0.5. The microstructure observed by TEM of InGaN films deposited on unheated substrates is highly columnar, with typical column widths of ~10 nm. The optical absorption spectra of InGaN/glass have a distinct absorption edge at the bandgap, but also high background absorption in the bandgap. InxGa1−xN grown on glass (x > 0.5) is conductive due to its high electron concentration. InN electron Hall mobilities > 20 cm2/Vs when grown at 400°C, and ~ 7 cm2/Vs on unheated substrates were obtained. The addition of GaN degraded the electrical properties of the films to a greater extent than it improved the transparency. As a result, the best transparent conductor films were pure InN which, when deposited at 400°C, were half as transparent in the green as an indium tin oxide film having the same sheet resistance.

scholarly journals Structural Optimization, Electronic Band Structure, Mechanical and Thermodynamics Properties of Fe3Al

2021 ◽  
pp. 1-11
Author(s):  
I. S. Okunzuwa ◽  
E. Aigbekaen Eddy
Keyword(s):  
Density Functional ◽  
Electronic Band Structure ◽  
Plane Waves ◽  
State Density ◽  
Structural Parameter ◽  
Mechanical And Thermal Properties ◽  
Energy Bands ◽  
Electronic Band ◽  
Salt Structure ◽  
Quantum Espresso

We calculated the structural, electronic, mechanical and thermal properties of Fe3Al semiconducting using Quantum ESPRESSO, an open source first principles code based on density-functional theory, plane waves, and pseudopotentials. Structural parameter results (equilibrium lattice parameters, bulk modulus and its derivative pressure) have been reported. The underestimated band gap is obtained along with higher state density and energy bands around the fermi level. Mechanical properties of the rock-salt structure of Fe3Al, such as, shear modulus (G), Young’s modulus (E), and Poisson’s ratio () were investigated. The thermodynamic parameters are also present. The results are in good agreement with the available experimental and other theoretical results.

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.

The n- and p-type thermoelectric response of a semiconducting Co-based quaternary Heusler alloy: a density functional approach

2019 ◽  
Vol 7 (25) ◽  
pp. 7664-7671 ◽  
Author(s):  
Enamullah Enamullah ◽  
Pil-Ryung Cha
Keyword(s):  
Electronic Structure ◽  
Thermoelectric Properties ◽  
Heusler Alloy ◽  
Density Functional ◽  
Transport Theory ◽  
Mechanical Stability ◽  
Functional Approach ◽  
Boltzmann Transport ◽  
Boltzmann Transport Theory ◽  
P Type

In the combined framework of density functional and Boltzmann transport theory, we have systematically studied the electronic structure, mechanical stability and thermoelectric properties of the semiconducting quaternary Heusler alloy, CoFeTiAl.

Terahertz conductivity of ultra high electron concentration 2DEGs in NTO/STO heterostructures

2016 ◽  
Author(s):  
Sara Arezoomandan ◽  
Hugo O. Condori Quispe ◽  
Ashish Chanana ◽  
Peng Xu ◽  
Ajay Nahata ◽  
...  
Keyword(s):  
Electron Concentration ◽  
High Electron ◽  
High Electron Concentration ◽  
Terahertz Conductivity
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