scholarly journals The Physical Properties of ThCr2Si2- Type Co-based Compound SrCo2Si2: An ab-initio Study

2021 ◽  
pp. 50-59
Keyword(s):  
Fermi Level ◽  
Density Functional ◽  
Mechanical Stability ◽  
High Energy ◽  
High Energy Region ◽  
Coating Materials ◽  
Functional Theory ◽  
Anisotropic Constant ◽  
The Density Functional Theory ◽  
Energy Package

In this article, we have studied the mechanical, electronic, and optical features of ThCr2Si2- type compound SrCo2Si2. The investigation has been done by using the first-principles method depend on the density functional theory (DFT) and the calculations were completed with the Cambridge Serial Total Energy Package (CASTEP) code. The optimized lattice parameters are well in accord with the existing synthesized values. The investigated elastic constants for this compound are positive which ensured the mechanical stability of this phase. The calculated values of Pugh’s ratio and Poisson’s ratio ensure the brittle character of SrCo2Si2. The universal anisotropic constant AU ensures the anisotropic behavior of SrCo2Si2.The softness nature of SrCo2Si2 is confirmed by the bulk modulus calculations. The overlapping of the valence band and conduction band near the Fermi level indicates the metallic nature of SrCo2Si2. At the Fermi level, the major contribution comes from Co-3d and Si-3p states. The large reflectivity in the high-energy region indicates that this compound might be useful as coating materials for reducing solar heating. The photoconductivity and absorption begins with zero photon energy which also ensures the metallic nature of SrCo2Si2.

Pressure-Induced Tunable Magnetism and Half-Metallic Stability in Co2FeGa Heusler Alloy

2013 ◽  
Vol 477-478 ◽  
pp. 1303-1306
Author(s):  
Qin Xiang Gao
Keyword(s):  
Fermi Level ◽  
First Principles ◽  
Density Functional ◽  
High Energy ◽  
First Principles Calculations ◽  
Half Metallicity ◽  
Functional Theory ◽  
Half Metallic ◽  
Heusler Compound ◽  
The Density Functional Theory

Using the first-principles calculations within the density functional theory (DFT), we have investigated the structure, magnetism and half-metallic stability of Co2FeGa Heusler compound under pressure from 0 to 50GPa. The results revel that the lattice constant is gradually shrank and total magnetic moment in per unit slightly decreased with increasing pressure, respectively. Moreover, with the increase of the pressure, the Fermi level will move towards high-energy orientation. When the pressure reaches at 30GPa the most stable half-metallicity is observed which the Fermi level is located at the middle of the spin-minority gap.

Computer Simulation of the Magnesium Silicide Polymorphs

2012 ◽  
Vol 170-173 ◽  
pp. 3312-3315
Author(s):  
Dong Chen ◽  
Chao Xu
Keyword(s):  
Optical Properties ◽  
Energy Region ◽  
High Performance ◽  
Density Functional ◽  
High Energy ◽  
Magnesium Silicide ◽  
High Energy Region ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Pseudo Potential

The anti-cotunnite magnesium silicide was constructed, and its absorption coefficient, dielectric function and loss function have been investigated through the plane-wave pseudo- potential calculations based on the density functional theory. In our scheme, we consider the Mg2Si crystal without defects or cracks. Significant features have been observed for the optical properties in the low-energy region and the high-energy region. The main focus of this paper is to determine the high-pressure optical properties of Mg2Si and find out if this material can be used as high-performance thermoelectric devices.

scholarly journals First Principles Study of Structural, Elastic, Electronic and Optical Features of the Non-centrosymmetric Superconductors SrMGe3 (Where M= Ir, Pt, and Pd)

2020 ◽  
pp. 16-28 ◽  
Keyword(s):  
Fermi Level ◽  
First Principles ◽  
Density Functional ◽  
Mechanical Stability ◽  
Lattice Parameters ◽  
Anisotropic Behavior ◽  
Metallic Behavior ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Atomic Populations

BaNiSn3-type superconductors SrIrGe3, SrPdGe3, and SrPtGe3 have a critical temperature of 1.80 K, 1.49K and 1.0K respectively have been reported recently. Employing the first-principles method based on the density functional theory, we have examined the physical properties including structural, elastic, electronic, and optical phenomena of all these structures. For all the phases our optimized lattice parameters are well accord to the experimental lattice parameters. The positive elastic constants of these compounds revealed that these superconductors possess mechanical stability in nature. The values of Pugh’s ratio and Poisson’s ratio ensured the brittle manner of these compounds and anisotropic behavior is ensured by the values of anisotropy factor. The soft nature of all compounds is confirmed by the bulk modulus analysis. The values of Vickers's hardness indicate that the rigidity decreased in the order of SrIrGe3>SrPtGe3>SrPdGe3. The overlapping of the conduction band and valence band at Fermi level indicates the zero band gaps and metallic nature of SrIrGe3, SrPdGe3, and SrPtGe3. The chief contribution around the Fermi level arises from Ir-5d, Ge-4s, 4p states for SrIrGe3 and Ge-4s, 4p states for SrPdGe3 and Pt-5d, Ge-4s, 4p for SrPtGe3 compound. The study of DOS, Mulliken atomic populations, and charge density ensured the existence of complex bonding in SrIrGe3, SrPdGe3, and SrPtGe3 with ionic, covalent, and metallic characteristics. The analysis of the dielectric function also ensured the metallic behavior of all these compounds.

Study on Electronic Structure of GaN under Pressure

2014 ◽  
Vol 900 ◽  
pp. 217-221
Author(s):  
Xing Xiang Ruan ◽  
Xian Hui Zhong ◽  
Fu Chun Zhang ◽  
Wei Hu Zhang
Keyword(s):  
Electronic Structure ◽  
Density Functional ◽  
Energy Gap ◽  
Potential Method ◽  
High Energy ◽  
Functional Theory ◽  
Conduction Bands ◽  
The Density Functional Theory ◽  
The Relationship ◽  
Pseudo Potential

A detailed theoretical study of electronic structure and optical properties of GaN under pressure was performed by the first-principles calculations of plane wave ultra-soft pseudo-potential method based on the density functional theory (DFT). The results indicate that Ga-N bond length becomes shorter and the valence bonds shift towards the low energy while the conduction bands towards high energy, the band gap becomes wider with the pressure increasing, and theoretical studies explained the relationship between the band edges, energy gap of GaN and pressure. In addition, the peak in band was cracked slightly, and the Ga 3d-N 2p hybridization was enhanced.

Graphene-Based Sensors for Monitoring Strain

2013 ◽  
Vol 3 (1) ◽  
pp. 74-83
Author(s):  
M. Mirnezhad ◽  
R. Ansari ◽  
H. Rouhi ◽  
M. Faghihnasiri
Keyword(s):  
Fermi Level ◽  
Band Gap ◽  
Strain Distribution ◽  
Density Functional ◽  
Tight Binding ◽  
Density Functional Theory Calculations ◽  
Generalized Gradient ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Gap Opening

The application of graphene as a nanosensor in measuring strain through its band structure around the Fermi level is investigated in this paper. The mechanical properties of graphene as well as its electronic structure are determined by using the density functional theory calculations within the framework of generalized gradient approximation. In the case of electronic properties, the simulations are applied for symmetrical and asymmetrical strain distributions in elastic range; also the tight-binding approach is implemented to verify the results. It is indicated that the energy band gap does not change with the symmetrical strain distribution but depend on the asymmetric strain distribution, increasing strain leads to band gap opening around the Fermi level.

scholarly journals Are boat transition states likely to occur in Cope rearrangements? A DFT study of the biogenesis of germacranes

2017 ◽  
Vol 13 ◽  
pp. 1969-1976 ◽  
Author(s):  
José Enrique Barquera-Lozada ◽  
Gabriel Cuevas
Keyword(s):  
Density Functional Theory ◽  
Transition State ◽  
Density Functional ◽  
Chair Conformation ◽  
High Energy ◽  
Functional Theory ◽  
Sigmatropic Rearrangements ◽  
The Density Functional Theory ◽  
Reaction Proceeds ◽  
Cope Rearrangements

It has been proposed that elemanes are biogenetically formed from germacranes by Cope sigmatropic rearrangements. Normally, this reaction proceeds through a transition state with a chair conformation. However, the transformation of schkuhriolide (germacrane) into elemanschkuhriolide (elemane) may occur through a boat transition state due to the final configuration of the elemanschkuhriolide, but this transition state is questionable due to its high energy. The possible mechanisms of this transformation were studied in the density functional theory frame. The mechanistic differences between the transformation of (Z,E)-germacranes and (E,E)-germacranes were also studied. We found that (Z,E)-germacranolides are significantly more stable than (E,E)-germacranolides and elemanolides. In the specific case of schkuhriolide, even when the boat transition state is not energetically favored, a previous hemiacetalization lowers enough the energetic barrier to allow the formation of a very stable elemanolide that is even more stable than its (Z,E)-germacrane.

A THEORETICAL STUDY OF UNSATURATED OLEFIN HYDROGENATION AND ISOMERIZATION ON Pd(111)

2008 ◽  
Vol 15 (03) ◽  
pp. 249-259 ◽  
Author(s):  
PATRICIA G. BELELLI ◽  
NORBERTO J. CASTELLANI
Keyword(s):  
Energy Barrier ◽  
Density Functional ◽  
Theoretical Study ◽  
High Energy ◽  
Slab Model ◽  
Functional Theory ◽  
Hydrogen Addition ◽  
High Energy Barrier ◽  
The Density Functional Theory ◽  
Cis And Trans

The addition of hydrogen to the carbon–carbon double bond of 2-butenes adsorbed on Pd (111) was studied within the density functional theory (DFT) and using a periodic slab model. For that purpose, the Horiuti–Polanyi mechanisms for both complete hydrogenation and isomerization were considered. The hydrogenation of cis and trans-2-butene to produce butane proceeds via the formation of eclipsed and staggered-2-butyl intermediates, respectively. In both cases, a relatively high energy barrier to produce the half-hydrogenated intermediate makes the first hydrogen addition the slowest step of the reaction. The competitive production of trans-2-butene from cis-2-butene requires the conversion from the eclipsed-2-butyl to the staggered-2-butyl isomer. As the corresponding energy barrier is relatively small and because the first of these isomers is less stable than the second, an easy conversion is predicted.

STRUCTURAL, ELASTIC AND ELECTRONIC PROPERTIES OF OXYGEN SUBSTITUTION IN CUBIC Zr3N4 AND Ti3N4

2013 ◽  
Vol 27 (18) ◽  
pp. 1350095 ◽  
Author(s):  
YI-MING CHEN ◽  
WEI CHENG ◽  
BIN LIAO ◽  
XU ZHANG
Keyword(s):  
Fermi Level ◽  
Electronic Properties ◽  
Density Functional ◽  
First Principles Calculations ◽  
Functional Theory ◽  
Shear Moduli ◽  
Young’S Moduli ◽  
The Density Functional Theory ◽  
Oxygen Substitution ◽  
Nitrogen Bond

The structural, elastic and electronic properties of O-doped and un-doped cubic Zr 3 N 4 and Ti 3 N 4 are studied by first principles calculations based on the density functional theory. The bulk and shear moduli, as well as Young's moduli, decrease after doping with oxygen, which is due to the lengthening of the metal-nitrogen bond as well as the inflation of the cell volume. The changes in elastic properties are consistent with available experimental results. Both nitrides change from brittle to ductile when doped with oxygen, and all materials can be regarded as being elastic isotropic. The band structure and density of states are calculated to discuss the electronic properties of O-doped cubic Zr 3 N 4 and Ti 3 N 4, the presence of oxygen has significant influence on the electronic structure near the Fermi level. The gap at Fermi level is vanished which confirms the metallic character when O is introduced into nitrides. It means that doping with oxygen will have important effects on the optical properties of Zr and Ti nitrides.

Quantum Chemical Investigation and Detonation Characterization of DNAZ·HCl

2014 ◽  
Vol 997 ◽  
pp. 77-80
Author(s):  
Biao Yan ◽  
Hong Yu Zhou
Keyword(s):  
Density Functional ◽  
Dft Method ◽  
High Energy ◽  
Detonation Pressure ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Equivalent Equation ◽  
Molecular Reactivity ◽  
Density Results

3,3-Dinitroazetidinium hydrochloride (DNAZ·HCl) is a novel insensitive high energy explosive. The density functional theory (DFT) method of the Amsterdam density functional (ADF) was used to calculate the geometry and frequencies. The detonation velocity (D) and detonation pressure (P) of DNAZ·HCl were estimated using the nitrogen equivalent equation according to the experimental density. Results showed that the initial decomposition step of DNAZ·HCl is the loss of NO2from C2 and Cl is the point of molecular reactivity.DandPare 6881.40 m·s-1and 20.85GPa, respectively.

scholarly journals Computational study of azole salts as high-energy materials

2017 ◽  
Vol 95 (6) ◽  
pp. 691-696 ◽  
Author(s):  
Zhou-Yu Meng ◽  
Feng-Qi Zhao ◽  
Si-Yu Xu ◽  
Xue-Hai Ju
Keyword(s):  
Density Functional ◽  
Computational Study ◽  
High Energy ◽  
Detonation Properties ◽  
Energy Materials ◽  
Functional Theory ◽  
Calculated Density ◽  
High Energy Materials ◽  
The Density Functional Theory ◽  
Impact Sensitivities

The crystal densities, heats of formation (HOFs), detonation properties, and impact sensitivities of a series of azole salts were investigated by the density functional theory and volume-based thermodynamics calculations. The HOFs of cations and anions and lattice energies were obtained based on the Born–Haber energy cycles. The detonation parameters (Q, D, and P) of 18 energetic salts have been calculated by the Kamlet–Jacobs equations with the calculated density and HOFs. The outcomes reflected that the hydroxylammonium cation has greater impact on the density and detonation properties of the azole salts than the hydrazine cation. Among all of the series salts under investigation, 2-amino-3-nitroamino-4,5-dinitropyrazole and 3-nitroamino-4,5-dinitropyrazole anions have greater HOFs and better detonation performances than other anions. In summary, the incorporations of all the cations studied here with the 2-amino-3-nitroamino-4,5-dinitropyrazole or 3-nitroamino-4,5-dinitropyrazole anions can be considered as potential high-energy salts.

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