Structural, Electronic, Elastic and Thermal Properties of Li2AgSb: First-Principles Calculations

2015 ◽  
Vol 70 (8) ◽  
pp. 611-618
Author(s):  
Ji-Hong Li ◽  
Xu-Hui Zhu ◽  
Yan Cheng ◽  
Guang-Fu Ji
Keyword(s):  
Thermal Properties ◽  
Band Structure ◽  
First Principles ◽  
Density Functional ◽  
Applied Pressure ◽  
Density Functional Theory Calculations ◽  
Debye Model ◽  
Partial Density ◽  
Functional Theory ◽  
Direct Band

AbstractBased on the first-principles density functional theory calculations combined with the quasi-harmonic Debye model, the pressure dependencies of the structural, elastic, electronic and thermal properties of Li2AgSb were systematically investigated. The calculated lattice parameters and unit cell volume of Li2AgSb at the ground state were in good agreement with the available experimental data. The obtained elastic constants, the bulk modulus and the shear modulus revealed that Li2AgSb is mechanically stable and behaves in a ductile manner under the applied pressure. The elasticity-relevant properties, the Young’s modulus and the Poisson’s ratio showed that pressure can enhance the stiffness of Li2AgSb and that Li2AgSb is mechanically stable up to 20 GPa. The characteristics of the band structure and the partial density of states of Li2AgSb were analysed, showing that Li2AgSb is a semiconductor with a direct band gap of 217 meV at 0 GPa and that the increasing pressure can make the band structure of Li2AgSb become an indirect one. Studies have shown that, unlike temperature, pressure has little effect on the heat capacity and the thermal expansion coefficient of Li2AgSb.

Electronic structure of the thermoelectric materials PbTe and AgPb18SbTe20 from first-principles calculations

2010 ◽  
Vol 25 (6) ◽  
pp. 1030-1036 ◽  
Author(s):  
Pengxian Lu ◽  
Zigang Shen ◽  
Xing Hu
Keyword(s):  
Band Structure ◽  
Thermoelectric Properties ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Partial Density ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Scanning Transmission ◽  
Linearized Augmented Plane Wave

To investigate the effects of substituting Ag and Sb for Pb on the thermoelectric properties of PbTe, the electronic structures of PbTe and AgPb18SbTe20 were calculated by using the linearized augmented plane wave based on the density-functional theory of the first principles. By comparing the differences in the band structure, the partial density of states (PDOS), the scanning transmission microscope, and the electron density difference for PbTe and AgPb18SbTe20, we explained the reason from the aspect of electronic structures why the thermoelectric properties of AgPb18SbTe20 could be improved significantly. Our results suggest that the excellent thermoelectric properties of AgPb18SbTe20 should be attributed in part to the narrowing of its band gap, band structure anisotropy, the much extrema and large DOS near Fermi energy, as well as the large effective mass of electrons. Moreover, the complex bonding behaviors for which the strong bonds and the weak bonds are coexisted, and the electrovalence and covalence of Pb–Te bond are mixed should also play an important role in the enhancement of the thermoelectric properties of the AgPb18SbTe20.

Electronic structure, elastic and thermal properties of semiconductor GaX (X = N, P, As, Sb) with zinc blende from first-principles calculation

2014 ◽  
Vol 28 (27) ◽  
pp. 1450183 ◽  
Author(s):  
Bingcheng Luo ◽  
Xiaowen Wu ◽  
Guowu Li
Keyword(s):  
Thermal Properties ◽  
Band Structure ◽  
Density Of States ◽  
Density Functional ◽  
First Principles Calculation ◽  
Functional Theory ◽  
Zinc Blende ◽  
Direct Band ◽  
Structure Density ◽  
Potential Methods

The band structure, density of states, elastic properties and thermal properties of semiconductor GaX (X = N , P , As , Sb ) with zinc blende were calculated by using the first principle plane-wave pseudo-potential methods based on density functional theory (DFT). The band structure and density of states for GaN , GaP , GaAs and GaSb show that GaX compounds are semiconductors with a direct band gap of 1.542, 1.445, 0.34 and 0.257 eV, respectively. The elastic constants and modulus are calculated showing that GaX are mechanically stable and GaN has the largest modulus. The anisotropy factor, internal-strain parameter, shear to bulk modulus and Poisson's ratio are also calculated indicating that GaX exhibit a brittle, anisotropic and plastic character. The dependencies of the Debye temperature, heat capacity, enthalpy, the entropy and free energy on temperature are also investigated. Comparisons with the available experiment and other theoretical calculation show reasonable agreement.

scholarly journals First-principles studies on band structure and mechanical properties of BiFeO3 ceramics under high pressure

2017 ◽  
Vol 11 (2) ◽  
pp. 120-126 ◽  
Author(s):  
Ramanathan Chandiramouli ◽  
Veerappan Nagarajan
Keyword(s):  
Mechanical Properties ◽  
Density Functional Theory ◽  
High Pressure ◽  
Band Structure ◽  
First Principles ◽  
Density Functional ◽  
Applied Pressure ◽  
Functional Theory ◽  
Increasing Trend ◽  
G Ratio

Mechanical properties and band structure of rhombohedral BiFeO3 nanostructures were studied using density functional theory for different pressures in the range from 0 to 50GPa. The elastic constant of BiFeO3 nanoceramics was determined and different moduli were calculated for various applied pressures. The bulk (B) and shear (G) modulus show an increasing trend on applied high pressure. The findings of the present work also confirm that the hardness of BiFeO3 increases with the applied pressure. The ductility of BiFeO3 nanostructure increases upon increasing the pressure, which is confirmed from Poisson?s ratio and B/G ratio. The band structure studies were also carried out under high pressure and showed that the band gap decreases upon increase in the applied pressure.

Understanding the advantage of hexagonal WO3 as an efficient photoanode for solar water splitting: a first-principles perspective

2016 ◽  
Vol 4 (29) ◽  
pp. 11498-11506 ◽  
Author(s):  
Taehun Lee ◽  
Yonghyuk Lee ◽  
Woosun Jang ◽  
Aloysius Soon
Keyword(s):  
Density Functional Theory ◽  
Band Gap ◽  
Water Splitting ◽  
Anode Material ◽  
First Principles ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Good Alternative ◽  
Functional Theory ◽  
Solar Water Splitting

Using first-principles density-functional theory calculations, we investigate the advantage of using h-WO3 (and its surfaces) over the larger band gap γ-WO3 phase for the anode in water splitting. We demonstrate that h-WO3 is a good alternative anode material for optimal water splitting efficiencies.

Probing the electronic structures of Con (n = 1–5) clusters on γ-Al2O3 surfaces using first-principles calculations

2017 ◽  
Vol 19 (5) ◽  
pp. 3679-3687 ◽  
Author(s):  
Tao Yang ◽  
Masahiro Ehara
Keyword(s):  
Density Functional Theory ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
First Principles Calculations ◽  
Functional Theory

Using density functional theory calculations, we discussed the geometric and electronic structures and nucleation of small Co clusters on γ-Al2O3(100) and γ-Al2O3(110) surfaces.

scholarly journals Strain Conditions for the Inverse Heusler Type Fully Compensated Spin-Gapless Semiconductor Ti2MnAl: A First-Principles Study

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2091 ◽  
Author(s):  
Tie Yang ◽  
Liyu Hao ◽  
Rabah Khenata ◽  
Xiaotian Wang
Keyword(s):  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
Theoretical Study ◽  
Debye Model ◽  
Pressure Effects ◽  
First Principles Calculation ◽  
Strain Condition ◽  
Functional Theory ◽  
Future Work

In this work, we systematically studied the structural, electronic, magnetic, mechanical and thermodynamic properties of the fully compensated spin-gapless inverse Heusler Ti2MnAl compound under pressure strain condition by applying the first-principles calculation based on density functional theory and the quasi-harmonic Debye model. The obtained structural, electronic and magnetic behaviors without pressure are well consistent with previous studies. It is found that the spin-gapless characteristic is destroyed at 20 GPa and then restored with further increase in pressure. While, the fully compensated ferromagnetism shows a better resistance against the pressure up to 30 GPa and then becomes to non-magnetism at higher pressure. Tetragonal distortion has also been investigated and it is found the spin-gapless property is only destroyed when c/a is less than 1 at 95% volume. Three independent elastic constants and various moduli have been calculated and they all show increasing tendency with pressure increase. Additionally, the pressure effects on the thermodynamic properties under different temperature have been studied, including the normalized volume, thermal expansion coefficient, heat capacity at constant volume, Grüneisen constant and Debye temperature. Overall, this theoretical study presents a detailed analysis of the physical properties’ variation under strain condition from different aspects on Ti2MnAl and, thus, can provide a helpful reference for the future work and even inspire some new studies and lead to some insight on the application of this material.

Preliminary First Principles Study Of Hf and Zr Aluminates as Replacement High-k Dielectrics

2001 ◽  
Vol 670 ◽  
Author(s):  
Michael Haverty ◽  
Atsushi Kawamoto ◽  
Gyuchang Jun ◽  
Kyeongjae Cho ◽  
Robert Dutton
Keyword(s):  
Density Functional Theory ◽  
Dielectric Constant ◽  
Bulk Density ◽  
First Principles ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Conduction Band Edge ◽  
Functional Theory ◽  
Trade Off ◽  
High K

ABSTRACTBulk Density Functional Theory calculations were performed on Hf and Zr substitutions for Al in κ-alumina. The lowest energy configuration found was an octahedrally coordinated Zr site. Zr dissolution was favorable with an enthalpy of -2eV/unit cell for forming Al1.875Zr0.125O3 from pure Zr and κ-alumina. Hf and Zr substitution for Al atoms introduced empty d-states below the conduction band edge reducing the Eg of pure κ-alumina (7.5eV) to 6.4-5.9eV. The edge of the valence band however remained fixed by the O p-state character. The substitution of Hf and Zr into the alumina structure may lead to a higher dielectric constant, but will also reduce Eg and result in a trade off in tunneling currents in devices.

First-Principles Analysis on Interaction between Dopant (Ga, Sb) and Contamination Metal Atoms in Ge Crystals

2013 ◽  
Vol 205-206 ◽  
pp. 417-421
Author(s):  
Tatsunori Yamato ◽  
Koji Sueoka ◽  
Takahiro Maeta
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Binding Energies ◽  
Functional Theory ◽  
Substitutional Site ◽  
Metal Impurities ◽  
Metal Atoms ◽  
Total Energies ◽  
Group 3

The lowest energetic configurations of metal impurities in 4throw (Sc - Zn), 5throw (Y - Cd) and 6throw (Hf - Hg) elements in Ge crystals were determined with density functional theory calculations. It was found that the substitutional site is the lowest energetic configuration for most of the calculated metals in Ge. The most stable configurations of dopant (Ga, Sb) - metal complexes in Ge crystals were also investigated. Following results were obtained. (1) For Ga dopant, 1st neighbor T-site is the most stable for metals in group 3 to 7 elements while substitutional site next to Ga atom is the most stable for metals in group 8 to 12 elements. (2) For Sb dopant, substitutional site next to Sb atom is the most stable for all calculated metals. Binding energies of the interstitial metalMiwith the substitutional dopantDswere obtained by the calculated total energies. The calculated results for Ge were compared with those for Si.

Thermodynamic Properties of CaSiO3 Perovskite at High Pressure and High Temperature

2009 ◽  
Vol 64 (5-6) ◽  
pp. 399-404 ◽  
Author(s):  
Zi-Jiang Liu ◽  
Xiao-Ming Tan ◽  
Yuan Guo ◽  
Xiao-Ping Zheng ◽  
Wen-Zhao Wu
Keyword(s):  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
High Pressures ◽  
Local Density ◽  
Harmonic Approximation ◽  
Debye Model ◽  
Functional Theory ◽  
Casio3 Perovskite ◽  
First Time

The thermodynamic properties of tetragonal CaSiO3 perovskite are predicted at high pressures and temperatures using the Debye model for the first time. This model combines the ab initio calculations within local density approximation using pseudopotentials and a plane wave basis in the framework of density functional theory, and it takes into account the phononic effects within the quasi-harmonic approximation. It is found that the calculated equation of state is in excellent agreement with the observed values at ambient condition. Based on the first-principles study and the Debye model, the thermal properties including the Debye temperature, the heat capacity, the thermal expansion and the entropy are obtained in the whole pressure range from 0 to 150 GPa and temperature range from 0 to 2000 K.

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