scholarly journals Three-dimensional metallic carbon allotropes with superhardness

2021 ◽  
Vol 10 (1) ◽  
pp. 1266-1276
Author(s):  
Qingyang Fan ◽  
Heng Liu ◽  
Li Jiang ◽  
Wei Zhang ◽  
Yanxing Song ◽  
...  
Keyword(s):  
Fermi Level ◽  
Dynamic Stability ◽  
First Principles ◽  
Mechanical Stability ◽  
Three Dimensional ◽  
First Principles Calculations ◽  
Charge Densities ◽  
Carbon Allotropes

Abstract Three novel three-dimensional orthorhombic carbon phases are proposed based on first-principles calculations in this work. These phases possess dynamic stability and mechanical stability and are theoretically more favorable in energy compared to most other carbon allotropes. The hardness levels of oP-C16, oP-C20, and oP-C24 are 47.5, 49.6, and 55.3 GPa, respectively, which are greater than those of T10, T18, and O12 carbon. In addition, although oP-C16, oP-C20, and oP-C24 are metals, their ideal shear strengths are also greater than those of common metals such as Cu, Fe, and Al. Due to p y electrons crossing the Fermi level, oP-C16, oP-C20, and oP-C24 show metallicity, and their charge densities of the band decomposition suggest that all the conductive directions of oP-C16, oP-C20, and oP-C24 are exhibited along the a- and b-axis, similar to C5.

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.

scholarly journals Rich p -type-doping phenomena in boron-substituted silicene systems

2020 ◽  
Vol 7 (12) ◽  
pp. 200723
Author(s):  
Hai Duong Pham ◽  
Wu-Pei Su ◽  
Thi Dieu Hien Nguyen ◽  
Ngoc Thanh Thuy Tran ◽  
Ming-Fa Lin
Keyword(s):  
Charge Transfer ◽  
Fermi Level ◽  
Charge Density ◽  
Electronic Properties ◽  
First Principles ◽  
Chemical Environment ◽  
First Principles Calculations ◽  
Density Distributions ◽  
Essential Properties ◽  
P Type

The essential properties of monolayer silicene greatly enriched by boron substitutions are thoroughly explored through first-principles calculations. Delicate analyses are conducted on the highly non-uniform Moire superlattices, atom-dominated band structures, charge density distributions and atom- and orbital-decomposed van Hove singularities. The hybridized 2 p z –3 p z and [2s, 2 p x , 2 p y ]–[3s, 3 p x , 3 p y ] bondings, with orthogonal relations, are obtained from the developed theoretical framework. The red-shifted Fermi level and the modified Dirac cones/ π bands/ σ bands are clearly identified under various concentrations and configurations of boron-guest atoms. Our results demonstrate that the charge transfer leads to the non-uniform chemical environment that creates diverse electronic properties.

scholarly journals Preferential proton conduction along a three-dimensional dopant network in yttrium-doped barium zirconate: a first-principles study

2018 ◽  
Vol 6 (45) ◽  
pp. 22721-22730 ◽  
Author(s):  
Kazuaki Toyoura ◽  
Weijie Meng ◽  
Donglin Han ◽  
Tetsuya Uda
Keyword(s):  
First Principles ◽  
Three Dimensional ◽  
Proton Conduction ◽  
Atomic Scale ◽  
Barium Zirconate ◽  
First Principles Calculations ◽  
First Principles Study

The atomic-scale picture of proton conduction in highly doped barium zirconate has theoretically been clarified using first-principles calculations.

Structural, mechanical and thermodynamic properties study on Mg–Y alloys from first-principles calculations

2020 ◽  
Vol 34 (25) ◽  
pp. 2050220
Author(s):  
Yingying Chen ◽  
Xilong Dou ◽  
Wenjie Zhu ◽  
Gang Jiang ◽  
Aijie Mao
Keyword(s):  
Thermodynamic Properties ◽  
First Principles ◽  
Mechanical Stability ◽  
Elastic Anisotropy ◽  
Crystal Structure Analysis ◽  
First Principles Calculations ◽  
Phonon Spectra ◽  
Volume Entropy ◽  
Ductile Behavior ◽  
Searching Method

The structures with different compositions of the binary Mg–Y alloys have been predicted by first-principles calculations combined with an unbiased Crystal structure Analysis by Particle Swarm Optimization (CALYPSO) structure searching method. The two already known stoichiometries alloys of Mg1Y1 with Pm-[Formula: see text] symmetry and Mg3Y1 with Fm-[Formula: see text] are confirmed, and a new stoichiometry alloy of Mg1Y3 with [Formula: see text] symmetry is proposed. The dynamical and mechanical stabilities for the three alloys at different pressures are investigated by phonon spectra and mechanical stability criteria, respectively. Subsequently, the bulk modulus, shear modulus, Young’s modulus, the brittleness/ductile behavior, the elastic anisotropy as well as Vickers hardness for the three alloys at 0 GPa are discussed in detail. The results show that the Mg1Y1, Mg3Y1 and Mg1Y3 alloys improve the hardness and stiffness compared with pure Mg, and Mg1Y3 alloy is of the best ductility in the three alloys. Meanwhile, the three alloys exhibit anisotropic. Moreover, the thermodynamic properties, such as Debye temperature, heat capacity at constant volume, entropy and Helmholtz free energy for the three stable alloys, are predicted and discussed.

Monolayer β-tellurene: a promising p-type thermoelectric material via first-principles calculations

Nanoscale ◽  
2019 ◽  
Vol 11 (39) ◽  
pp. 18116-18123 ◽  
Author(s):  
David Kipkemoi Sang ◽  
Teng Ding ◽  
Meng Nan Wu ◽  
Yu Li ◽  
Junqin Li ◽  
...  
Keyword(s):  
Thermoelectric Material ◽  
First Principles ◽  
First Principles Calculations ◽  
Charge Densities ◽  
P Type

Side and top views of monolayer 2D-β-Tellurene with difference charge densities (DCD).

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.

scholarly journals Assessing the role of hydrogen in Fermi-level pinning in chalcopyrite and kesterite solar absorbers from first-principles calculations

2018 ◽  
Vol 123 (16) ◽  
pp. 161408 ◽  
Author(s):  
J. B. Varley ◽  
V. Lordi ◽  
T. Ogitsu ◽  
A. Deangelis ◽  
K. Horsley ◽  
...  
Keyword(s):  
Fermi Level ◽  
First Principles ◽  
First Principles Calculations ◽  
Fermi Level Pinning ◽  
Solar Absorbers

First-Principles Study of the Elastic Properties of Hexagonal Phase ScAx (A=H, He)

2013 ◽  
Vol 690-693 ◽  
pp. 1723-1727
Author(s):  
Kai Min Fan ◽  
Li Yang ◽  
Jing Tang ◽  
Qing Qiang Sun ◽  
Xiao Tao Zu
Keyword(s):  
Elastic Modulus ◽  
Shear Modulus ◽  
Bulk Modulus ◽  
First Principles ◽  
Poisson’S Ratio ◽  
Hexagonal Phase ◽  
Poisson's Ratio ◽  
First Principles Calculations ◽  
Charge Densities ◽  
Change Mechanism

First-principles calculations are performed to investigate the Young’s modulus, bulk modulus, shear modulus and Poisson’s ratio of hexagonal phase ScAx(A=H, He), where x=0, 0.0313, 0.125 and 0.25, represent the ratio of interstitial atoms A (A=H, He) to Sc atoms. The influences of hydrogen concentrations and helium concentrations on elastic modulus and Poisson’s ratio of ScAx(A=H, He) have been studied. The results indicate that hydrogen and helium have different effects on the elastic modulus of hexagonal phase scandium. The change mechanism of the Poisson’s ratio with the variation of the x ranging from 0 to 0.25 has also been studied in hexagonal phase ScAx(A=H, He). In addition, the changes in the charge densities of ScAxdue to the presence of hydrogen and helium have been calculated.

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