Na2HeO: A possible helium compound from first-principles study

2020 ◽  
Vol 09 (01) ◽  
pp. 2050001 ◽  
Author(s):  
Z. B. Zou ◽  
R. Q. Wu ◽  
Y. F. Zhao
Keyword(s):  
First Principles ◽  
Local Minimum ◽  
Phonon Dispersion ◽  
Electronic Band Structure ◽  
Energy Calculation ◽  
First Principle ◽  
Chemical Formula ◽  
Charge Density Distribution ◽  
Electronic Band ◽  
Wide Gap

By first-principle study, we propose a possible stable helium-based compound with chemical formula of Na2HeO. It has a structure of space group [Formula: see text]. Energy calculation indicates that it has a local minimum with a lattice constant [Formula: see text] Å. Electronic band structure suggests that it is a wide gap insulator. Analysis on Hirshfeld charges and charge density distribution shows a chemical bond formed between O and He atoms in this structure. Results from both elastic constants and phonon dispersion indicate that this compound in the proposed structure is both mechanically and dynamically stable.

scholarly journals Electronic Band Structure Variations in the Ceria Doped Zirconia: A First Principles Study

Materials ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1238 ◽  
Author(s):  
Sahar Ramin Gul ◽  
Matiullah Khan ◽  
Yi Zeng ◽  
Maohua Lin ◽  
Bo Wu ◽  
...  
Keyword(s):  
Band Structure ◽  
Band Gap ◽  
First Principles ◽  
Zirconium Dioxide ◽  
Doping Concentration ◽  
Electronic Band Structure ◽  
Valence Band Maximum ◽  
First Principle ◽  
Electronic Band ◽  
Photo Response

Using first principle calculations, the effect of Ce with different doping concentrations in the network of Zirconium dioxide (ZrO2) is studied. The ZrO2 cell volume linearly increases with the increasing Ce doping concentration. The intrinsic band gap of ZrO2 of 5.70 eV reduces to 4.67 eV with the 2.08% Ce doping. In 4.16% cerium doped ZrO2, the valence band maximum and conduction band minimum come closer to each other, about 1.1 eV, compared to ZrO2. The maximum band gap reduction of ZrO2 is observed at 6.25% Ce doping concentration, having the value of 4.38 eV. No considerable shift in the band structure is found with further increase in the doping level. The photo-response of the ZrO2 is modulated with Ce insertion, and two distinct modifications are observed in the absorption coefficient: an imaginary part of the dielectric function and conductivity. A 2.08% Ce-doped ZrO2 modeled system reduces the intensities of peaks in the optical spectra while keeping the peaks of intrinsic ZrO2. However, the intrinsic peaks related to ZrO2 completely vanish in 4.16%, 6.25%, 8.33%, and 12.5% Ce doped ZrO2, and a new absorption hump is created.

Ab-Initio Investigation of Strain Effects on the Physical Properties of PdVTe Alloy

2021 ◽  
Author(s):  
Khodja Djamila ◽  
Djaafri Tayeb ◽  
Djaafri Abdelkader ◽  
Bendjedid Aicha ◽  
Hamada Khelifa ◽  
...  
Keyword(s):  
Optical Properties ◽  
Density Of States ◽  
Phonon Dispersion ◽  
Electronic Band Structure ◽  
Debye Model ◽  
Full Potential ◽  
Electronic Band ◽  
Metallic Behavior ◽  
Strain Effects ◽  
Half Metallic

The investigations of the strain effects on magnetism, elasticity, electronic, optical and thermodynamic properties of PdVTe half-Heusler alloy are carried out using the most accurate methods to electronic band structure, i.e. the full-potential linearized augmented plane wave plus a local orbital (FP-LAPW + lo) approach. The analysis of the band structures and the density of states reveals the Half-metallic behavior with a small indirect band gap Eg of 0.51 eV around the Fermi level for the minority spin channels. The study of magnetic properties led to the predicted value of total magnetic moment µtot = 3µB, which nicely follows the Slater–Pauling rule µtot = Zt -18. Several optical properties are calculated for the first time and the predicted values are in line with the Penn model. It is shown from the imaginary part of the complex dielectric function that the investigated alloy is optically metallic. The variations of thermodynamic parameters calculated using the quasi-harmonic Debye model, accord well with the results predicted by the Debye theory. Moreover, the dynamical stability of the investigated alloy is computed by means of the phonon dispersion curves, the density of states, and the formation energies. Finally, the analysis of the strain effects reveals that PdVTe alloy preserves its ferromagnetic half metallic behavior, it remains mechanically stable, the ionic nature dominates the atomic bonding, and the thermodynamic and the optical properties keep the same features in a large interval of pressure.

scholarly journals Physical Properties Investigations of Ternary-Layered Carbides M2PbC (M = Ti, Zr and Hf): First-Principles Calculations

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1445
Author(s):  
Tahani A. Alrebdi ◽  
Mohammed Benali Kanoun ◽  
Souraya Goumri-Said
Keyword(s):  
Elastic Constants ◽  
First Principles ◽  
Mechanical Stability ◽  
Electronic Band Structure ◽  
Max Phase ◽  
Mechanical And Thermal Properties ◽  
First Principles Calculations ◽  
Electronic Band ◽  
Bonding Properties ◽  
Structure Density

We investigated structure optimization, mechanical stability, electronic and bonding properties of the nanolaminate compounds Ti2PbC, Zr2PbC, and Hf2PbC using the first-principles calculations. These structures display nanolaminated edifices where MC layers are interleaved with Pb. The calculation of formation energies, elastic moduli and phonons reveal that all MAX phase systems are exothermic, and are intrinsically and dynamically stable at zero and under pressure. The mechanical and thermal properties are reported with fundamental insights. Results of bulk modulus and shear modulus show that the investigated compounds display a remarkable hardness. The elastic constants C11 and C33 rise more quickly with an increase in pressure than that of other elastic constants. Electronic and bonding properties are investigated through the calculation of electronic band structure, density of states, and charge densities.

First-principles studies of the elastic and magnetic properties of monolayer CrN

2021 ◽  
Author(s):  
Tai Ma ◽  
Jia Wang ◽  
Xu Li ◽  
Min Pu
Keyword(s):  
Magnetic Properties ◽  
Band Structure ◽  
First Principles ◽  
Electronic Band Structure ◽  
Strain Analysis ◽  
Exchange Interactions ◽  
Potential Method ◽  
Graphene Monolayer ◽  
Electronic Band ◽  
Spin Electronics

Two-dimensional (2D) materials with robust ferromagnetism properties have high potentials for application in the field of spintronics. However, extensively pursued 2D sheets, including pure graphene, monolayer BN, and layered transition metal dichalcogenides, are either nonmagnetic or weakly magnetic. The elastic, electronic and magnetic properties of monolayer CrN are calculated using the plane wave pseudo potential method based on first-principles density function theory. Upon determining through calculation that the structure of the monolayer CrN nanosheet is stable, its layer modulus [Formula: see text] shows that its strain resistance is stronger than that of graphene. Through strain analysis, materials with a monolayer CrN type of structure can be obtained. It is determined that 10% of the change in equilibrium area is still applicable to the 2D EOS, showing that this structure is quite stable. The spin-polarized electronic band structure is also calculated under different plane symmetry strains. The plane strain can be used to effectively adjust the metallic and magnetic properties of the material. Analyses of the band structure and density of states reveal that this material is half-metallic, where the origin of the ferromagnetism is related to [Formula: see text]–[Formula: see text] exchange interactions between the Cr and N atoms. Monolayer CrN has semimetallic properties and strong ferromagnetic (FM) properties. The FM effect can enhance the stability of the material. The results show that monolayer CrN is a semimetallic material with good elastic properties and a strong FM property. This material is therefore expected to have good application rospects in the field of spin electronics.

First-Principles Study of the New Half-Metallic Ferromagnetic Quaternary-Heusler Alloys NaXNO (X=Ca, Sr, Ba)

SPIN ◽  
2020 ◽  
Vol 10 (03) ◽  
pp. 2050022 ◽  
Author(s):  
K. Belkacem ◽  
Y. Zaoui ◽  
S. Amari ◽  
L. Beldi ◽  
B. Bouhafs
Keyword(s):  
Magnetic Properties ◽  
Density Of States ◽  
First Principles ◽  
Density Functional ◽  
Heusler Alloys ◽  
Exchange Potential ◽  
Energy Calculation ◽  
Full Potential ◽  
Electronic Band ◽  
Half Metallic

The first-principles approach based on density functional theory (DFT) and the full-potential linearized augmented plane-wave method were employed to investigate the structural, elastic, electronic and magnetic properties of Na[Formula: see text]NO ([Formula: see text], Sr and Ba) quaternary half-Heusler alloys. The generalized gradient approximation (GGA) as parameterized by Perdew, Burke and Ernzerhof (PBE) and the modified Becke–Johnson exchange potential were used. As far as we know, we present our results which for the first time quantitatively account for the electronic structures and magnetic properties of Na[Formula: see text]NO ([Formula: see text], Sr and Ba) quaternary half-Heusler alloys. From the total energy calculation using three possible atomic configurations ([Formula: see text], [Formula: see text] and [Formula: see text]), it is found that the Na[Formula: see text]NO ([Formula: see text], Sr and Ba) quaternary half-Heusler alloys are more stable in the ferromagnetic [Formula: see text]-phase. From our estimated elastic constants [Formula: see text], it is found that all the considered Heusler alloys are mechanically stable in the [Formula: see text]-phase. We have also investigated the robustness of the half-metallicity with respect to the variation of lattice constants in these alloys. We have found that these alloys are half-metallic ferromagnets (HMFs) with a magnetic moment of 2[Formula: see text][Formula: see text] per formula unit at their equilibrium volumes. The spin-polarized electronic band structure and density of states of these quaternary half-Heusler alloys calculated by GGA (mBJ-GGA) show that the minority spin channels have metallic nature and the majority spin channels have a semiconductor character with half-metallic gaps of 0.49[Formula: see text]eV (2.17[Formula: see text]eV), 0.72[Formula: see text]eV (2.28[Formula: see text]eV) and 0.96[Formula: see text]eV (2.22[Formula: see text]eV) for NaCaNO, NaSrNO and NaBaNO quaternary half-Heusler alloys, respectively. Analysis of the density of states and the spin charge density of these quaternary alloys indicates that their magnetic moments mainly originate from the strong spin-polarization of 2[Formula: see text] states of N atoms and O atoms.

scholarly journals A First-Principles Study of Nonlinear Elastic Behavior and Anisotropic Electronic Properties of Two-Dimensional HfS2

Nanomaterials ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 446
Author(s):  
Mahdi Faghihnasiri ◽  
Aidin Ahmadi ◽  
Samaneh Alvankar Golpayegan ◽  
Saeideh Garosi Sharifabadi ◽  
Ali Ramazani
Keyword(s):  
Electronic Properties ◽  
First Principles ◽  
Electronic Band Structure ◽  
Hexagonal Phase ◽  
Strain Engineering ◽  
Elastic Behavior ◽  
Potential Candidate ◽  
Two Dimensional ◽  
Electronic Band ◽  
Wide Range

We utilize first principles calculations to investigate the mechanical properties and strain-dependent electronic band structure of the hexagonal phase of two dimensional (2D) HfS2. We apply three different deformation modes within −10% to 30% range of two uniaxial (D1, D2) and one biaxial (D3) strains along x, y, and x-y directions, respectively. The harmonic regions are identified in each deformation mode. The ultimate stress for D1, D2, and D3 deformations is obtained as 0.037, 0.038 and 0.044 (eV/Ang3), respectively. Additionally, the ultimate strain for D1, D2, and D3 deformation is obtained as 17.2, 17.51, and 21.17 (eV/Ang3), respectively. In the next step, we determine the second-, third-, and fourth-order elastic constants and the electronic properties of both unstrained and strained HfS2 monolayers are investigated. Our findings reveal that the unstrained HfS2 monolayer is a semiconductor with an indirect bandgap of 1.12 eV. We then tune the bandgap of HfS2 with strain engineering. Our findings reveal how to tune and control the electronic properties of HfS2 monolayer with strain engineering, and make it a potential candidate for a wide range of applications including photovoltaics, electronics and optoelectronics.

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