scholarly journals Pressure Effect of the Mechanical, Electronics and Thermodynamic Properties of Mg-B Compounds: A First-Principles Investigation

2021 ◽  
Author(s):  
GuoWei Zhang ◽  
Chao Xu ◽  
MingJie Wang ◽  
Hong Xu ◽  
Ying Dong ◽  
...  
Keyword(s):  
Thermodynamic Properties ◽  
Boron Content ◽  
Structural Parameters ◽  
Linear Thermal Expansion ◽  
Debye Model ◽  
Total Density ◽  
First Principle ◽  
Volume Deformation ◽  
Temperature And Pressure ◽  
Total Density Of States

Abstract First principle calculations were performed to investigate the structural, mechanical, electronic properties, and thermodynamic properties of three binary Mg-B compounds under pressure, by using the first principle method. The results implied that the structural parameters and the mechanical properties of the Mg-B compounds without pressure are well matched with the obtainable theoretically simulated values and experimental data. The obtained pressure–volume and energy–volume revealed that the three Mg-B compounds were mechanically stable, and the volume variation decreases with an increase in the boron content. The shear and volume deformation resistance indicated that the elastic constant C ij and bulk modulus B increased when the pressure increased up to 40 GPa, and that MgB 7 had the strongest capacity to resist shear and volume deformation at zero pressure, which indicated the highest hardness. Meanwhile, MgB 4 exhibited a ductility transformation behaviour at 30 GPa, and MgB 2 and MgB 7 displayed a brittle nature under all the considered pressure conditions. The anisotropy of the three Mg-B compounds under pressure were arranged as follows: MgB 4 > MgB 2 > MgB 7. Moreover, the total density of states (TDOS) varied slightly and decreased with an increase in the pressure. The Debye temperature Θ D of the Mg-B compounds gradually increased with an increase in the pressure and the boron content. The temperature and pressure dependence of the heat capacity and the linear thermal expansion coefficient α were both obtained on the basis of Debye model under increased pressure from 0GPa to 40 GPa and increased temperatures. This paper brings a convenient understanding of the magnesium-boron alloys.

scholarly journals Pressure effect of the mechanical, electronics and thermodynamic properties of Mg–B compounds A first-principles investigations

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
GuoWei Zhang ◽  
Chao Xu ◽  
MingJie Wang ◽  
Ying Dong ◽  
FengEr Sun ◽  
...  
Keyword(s):  
Thermodynamic Properties ◽  
First Principles ◽  
Boron Content ◽  
Structural Parameters ◽  
Debye Model ◽  
Total Density ◽  
First Principle ◽  
Volume Deformation ◽  
Temperature And Pressure ◽  
Total Density Of States

AbstractFirst principle calculations were performed to investigate the structural, mechanical, electronic properties, and thermodynamic properties of three binary Mg–B compounds under pressure, by using the first principle method. The results implied that the structural parameters and the mechanical properties of the Mg–B compounds without pressure are well matched with the obtainable theoretically simulated values and experimental data. The obtained pressure–volume and energy–volume revealed that the three Mg–B compounds were mechanically stable, and the volume variation decreases with an increase in the boron content. The shear and volume deformation resistance indicated that the elastic constant Cij and bulk modulus B increased when the pressure increased up to 40 GPa, and that MgB7 had the strongest capacity to resist shear and volume deformation at zero pressure, which indicated the highest hardness. Meanwhile, MgB4 exhibited a ductility transformation behaviour at 30 GPa, and MgB2 and MgB7 displayed a brittle nature under all the considered pressure conditions. The anisotropy of the three Mg–B compounds under pressure were arranged as follows: MgB4 > MgB2 > MgB7. Moreover, the total density of states varied slightly and decreased with an increase in the pressure. The Debye temperature ΘD of the Mg–B compounds gradually increased with an increase in the pressure and the boron content. The temperature and pressure dependence of the heat capacity and the thermal expansion coefficient α were both obtained on the basis of Debye model under increased pressure from 0 to 40 GPa and increased temperatures. This paper brings a convenient understanding of the magnesium–boron alloys.

scholarly journals THE PHONON SPECTRUM OF THE OCTAGONAL TILING

1993 ◽  
Vol 07 (06n07) ◽  
pp. 1505-1525 ◽  
Author(s):  
J. LOS ◽  
T. JANSSEN ◽  
F. GÄHLER
Keyword(s):  
Specific Heat ◽  
Density Of States ◽  
Phonon Spectrum ◽  
Low Frequency ◽  
Debye Model ◽  
Square Lattice ◽  
Total Density ◽  
Unit Cells ◽  
Linear Behaviour ◽  
Total Density Of States

A study of the phonon spectrum of the octagonal tiling is presented, by calculating and analysing the properties of the spectrum of perfect and randomized commensurate approximants with unit cells containing up to 8119 vertices. The total density of states, obtained by numerical integration over the Brillouin zone, exhibits much structure, and in the low frequency range of the spectrum there is deviation from the normal linear behaviour in the form of pseudogaps. For randomized approximants these pseudogaps disappear and the density of states is globally smoothened. It turns out that the widths of the gaps in the dispersion vanish in the low frequency limit. Therefore the scaling behaviour of the lowest branches tends to the behaviour of an absolutely continuous spectrum, which is not the case at higher frequencies. As an application, the vibrational specific heat of the different tiling models is calculated and compared to the specific heat of a square lattice and of a Debye model.

First-Principles Calculations of Elastic and Thermodynamic Properties of Cubic CdTe

2011 ◽  
Vol 268-270 ◽  
pp. 886-891
Author(s):  
Ben Hai Yu ◽  
Dong Chen
Keyword(s):  
Experimental Data ◽  
Heat Capacity ◽  
Thermodynamic Properties ◽  
Bulk Modulus ◽  
First Principles ◽  
Debye Model ◽  
First Principles Calculations ◽  
Lattice Constants ◽  
Temperature And Pressure ◽  
The Relationship

the equilibrium lattice constants, elastic and thermodynamic properties of cubic CdTe are systemically investigated at high temperature using the plane-wave pseudopotential method as well as the quasi-harmonic Debye model. The bulk modulus of CdTe are calculated as a function of temperature up to 1000K, the relationship between bulk modulusBand pressure is also obtained. The results gained from this model will provide overall predictions accurately for the temperature and pressure dependence of various quantities such as the bulk modulus, the heat capacity and the thermal expansion coefficient. More over, the dependences between Debye temperature and temperature are also successfully obtained. Our results are compared with the experimental data and discussed in light of previous works.

The structures, phase transition and elastic and thermodynamic properties of ZnS from first-principles calculations

2021 ◽  
pp. 2150143
Author(s):  
Bo Li ◽  
Weiyi Ren
Keyword(s):  
Phase Transition ◽  
Thermodynamic Properties ◽  
Bulk Modulus ◽  
First Principles ◽  
Density Functional ◽  
Mechanical Stability ◽  
Theoretical Data ◽  
Debye Model ◽  
Volume Curve ◽  
Temperature And Pressure

The phase transition of zinc sulfide (ZnS) from Zinc-blende (ZB) to a rocksalt (RS) structure and the elastic, thermodynamic properties of the two structures under high temperature and pressure are investigated by first-principles study based on the pseudo-potential plane-wave density functional theory (DFT) combined with the quasi-harmonic Debye model. The lattice constant [Formula: see text], bulk modulus [Formula: see text] and the pressure derivative of bulk modulus [Formula: see text]’ of the two structures are calculated. The results are in good agreement with experimental results and the other theoretical data. From the energy–volume curve, enthalpy equal principle and mechanical stability criterion, the transition pressures from the ZB to the RS structure are 16.83, 16.96 and 16.61 GPa, respectively. The three results and the experimental values 14.7–18.1, 16 GPa are very close to each other. Then the elastic properties are also calculated under the pressure ranging from 0 to 30 GPa. Finally, through the quasi-harmonic Debye model, the thermodynamic properties dependence of temperature and pressure in the ranges between 0–1600 K and 0–30 GPa are obtained successfully.

scholarly journals First Principle Calculations for Silver Halides AgBr, AgCl, and AgF

2021 ◽  
Vol 9 (2) ◽  
pp. 71-75
Author(s):  
Akram H. Taha
Keyword(s):  
Electronic Structures ◽  
Density Functional ◽  
Total Density ◽  
First Principle ◽  
Silver Halides ◽  
Functional Theory ◽  
First Principle Calculations ◽  
Almost All ◽  
Total Density Of States ◽  
Good Agreement

Density functional theory (DFT) coupled with ) method are carried out to calculate the electronic structures of AgX (X; Br, Cl, and F). The effect of hybridizing between 4d orbital of Ag element and the p orbitals of the X in the valence band plays a very important role in the total density of states configuration. The electronic structure has been studied and all results were compared with the experimental and theoretical values. The importance of this work is that there is insufficient studies of silver halides corresponding the great importance of these compounds. Almost all the results were consistent with the previous studies mentioned here. We found the band gap of AgX to be 2.343 eV, 2.553 eV, and 1.677 eV for AgBr, AgCl, and AgF respectively which are in good agreement with the experimental results.      

Thermodynamic Properties of AlNi Intermetallics under High Pressure

2011 ◽  
Vol 268-270 ◽  
pp. 275-279
Author(s):  
Hai Yan Wang ◽  
Dong Xia Xu ◽  
Jin Bang Yu ◽  
Xu Sheng Li ◽  
Qian Ku Hu
Keyword(s):  
Thermodynamic Properties ◽  
Density Functional ◽  
Linear Thermal Expansion ◽  
Debye Model ◽  
Lattice Parameter ◽  
Relative Volume ◽  
Full Potential ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Calculated Lattice Parameter

The thermodynamic properties of AlNi are investigated by the full-potential linearized muffin-tin orbital (FP-LMTO) scheme within the generalized gradient approximation correction (GGA) in the frame of density functional theory. The calculated lattice parameter and bulk modulus are in excellent agreement with the experimental and other calculated results. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the dependences of relative volumeV/V0on pressureP, cell volumeVon temperatureT, linear thermal expansion α and specific heatCVon temperature and pressure are successfully obtained.

Study of the Mechanical and Thermodynamic Properties on NiAl and Ni3Al

2014 ◽  
Vol 584-586 ◽  
pp. 1256-1263 ◽  
Author(s):  
Yong He Deng
Keyword(s):  
Thermodynamic Properties ◽  
Bulk Modulus ◽  
Intermetallic Compounds ◽  
Mutual Influence ◽  
Debye Model ◽  
First Principle ◽  
Mechanical Parameters ◽  
Wave Method ◽  
Plane Wave Method ◽  
Equilibrium Volume

The stuctural, elastic and thermodynamic properties of B2-NiAl and L12-Ni3Al intermetallic compounds are systemically investigated. Using a first principle pseudopotential plane-wave method, several basic mechanical parameters of B2-NiAl and L12-Ni3Al crystals, such as the equilibrium volume, the bulk modulus, the elastic constants, the Zener anisotropy factor, the Poisson’s ratio, the Young’s modulus and isotropic shear modulus are firstly calculated. And then the temperature dependence of the equilibrium volume, the bulk modulus, the thermal expansion coefficient, the heat capacity, the Debye temperature and the Grüneisen parameter are further evaluated in the framework of a quasi-harmonic Debye model. Finally, a special attention is paied on the mutual influence of pressure and temperature on mechenical and thermodynanic properties of B2-NiAl and L12-Ni3Al intermetallic compounds in the range of 0-20 GPa and 0-1000 K.

Effect of Carbon Doped in BN on Thermodynamic Properties

2013 ◽  
Vol 706-708 ◽  
pp. 85-89
Author(s):  
Jing Ao ◽  
Ai Ling Ding ◽  
Chun Mei Li ◽  
Feng Li ◽  
Jin Wang ◽  
...  
Keyword(s):  
Thermodynamic Properties ◽  
Density Functional ◽  
Local Density ◽  
Debye Model ◽  
Relative Volume ◽  
Density Approximation ◽  
Virtual Crystal Approximation ◽  
Functional Theory ◽  
Carbon Doped ◽  
Temperature And Pressure

The thermodynamic properties of (B1-xCx)(N1-xCx) (x=0, 0.25, 0.5) are calculated by the ultra-soft pseud-potentials within local density approximation in frame of density functional theory with virtual crystal approximation and using the quasi-harmonic Debye model. The normalized relative volume V/V0, bulk modulus, thermal expansion coefficient α and heat capacity were computed with different temperature and pressure. Meanwhile the lower limit of the thermal conductivity κmin is also examined in details.

scholarly journals First-Principles Investigation of Structural, Electronic, and Room Temperature Ferromagnetism in Si-Doped Monolayer BN

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Ahemedin Abedea Ajaybu ◽  
Sintayehu Mekonnen Hailemariam
Keyword(s):  
Density Functional ◽  
Room Temperature ◽  
Structural Parameters ◽  
Room Temperature Ferromagnetism ◽  
Total Density ◽  
Ferromagnetic Transition ◽  
Functional Theory ◽  
Spin Polarized ◽  
Si Doped ◽  
Total Density Of States

We performed spin-polarized density functional theory (DFT) to investigate the structural, electronic, and magnetic properties of silicon- (Si-) doped monolayer boron nitride (BN). The present study revealed that structural parameters like bond length, bond angle, and lattice parameters increase as Si-doped in the B site of monolayer BN. However, the bandgap of monolayer BN is reduced in the presence of the Si dopant. Moreover, the obtained magnetic moment and analysis of the total density of states (TDOS) show that Si-doped monolayer BN displays ferromagnetism. The calculated ferromagnetic transition temperature (Tc) value for Si concentration of 12.5% is 476 K which exceeds room temperature. The findings are avenues to enhance the application of monolayer BN for spintronics.

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