Site occupation, phase stability, crystal and electronic structures of the doped S phase (Al2CuMg)

2016 ◽  
Vol 30 (24) ◽  
pp. 1650165 ◽  
Author(s):  
Jianglong Gu ◽  
Huimin Gu ◽  
Yuchun Zhai ◽  
Peihua Ma
Keyword(s):  
Performance Optimization ◽  
Electronic Structures ◽  
Density Functional ◽  
S Phase ◽  
Mg Alloys ◽  
Theoretical Understanding ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
And Performance ◽  
Impurity Elements

The S phase (Al2CuMg) is an important strengthening phase for the Al–Cu–Mg alloys, which are widely used in the aerospace and transportation industries. The commonly added alloying elements (Mn, Ti, Zr) and the impurity elements (Fe and Si) in the Al–Cu–Mg alloys are always found in the S phase. First-principles calculations based on the density functional theory (DFT) were used to investigate the influence of doping Mn, Ti, Zr, Fe and Si elements on the S phase. Key findings demonstrated that these elements prefer to occupy different atomic sites in the S phase. Ti and Zr improved the structural stability of the S phase. The bulk modulus of the Fe, Si, Ti and Zr doped S phases becomes larger than that of the pure S phase. Both the crystal and electronic structures of the S phase are affected by the dopants. The results of this study provide a better theoretical understanding of the S phase, providing guidance for improved composition design and performance optimization of Al–Cu–Mg alloys.

First-principles study on the effects of V, Nb, Cd, Ag, Ge and Sb doped in Al2CuMg phase of Al–Zn–Mg–Cu alloy

2021 ◽  
pp. 2150478
Author(s):  
Bingkang Li ◽  
Junkai Wang ◽  
Chuan-Hui Zhang
Keyword(s):  
First Principles ◽  
Performance Optimization ◽  
Density Functional ◽  
Covalent Bond ◽  
Mg Alloys ◽  
Partial Density ◽  
Theoretical Understanding ◽  
Cu Alloy ◽  
Sb Doping ◽  
And Performance

The [Formula: see text] phase (Al2CuMg) is an important strengthening phase for the Al–Zn–Cu–Mg alloys, which are widely used in the aerospace and transportation industries. First-principles calculations based on the density functional theory were used to investigate the effects of doping V, Nb, Cd, Ag, Ge and Sb elements on the [Formula: see text] phase. The results demonstrate that Ag atom can spontaneously dope into the [Formula: see text] phase. Ge and Sb doping can improve the toughness and plasticity of the [Formula: see text] phase. And doping Ge, V or Nb can reduce the anisotropy of the Al2CuMg phase. The hardness of the Nb, V, Cd and Ag doped structures become larger than that of the pristine structure. The results of orbital hybridization in the partial density of states (PDOS) and the distribution in electron density difference (EDD) confirmed that the effect of doping elements and Al atoms has the greatest impact on the performance of the system, and the strength of the covalent bond of the system affects the main aspects of brittleness. This study provides a better theoretical understanding of the doped [Formula: see text] phase, providing guidance for improved composition design and performance optimization of Al–Zn–Cu–Mg alloys.

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.

Density Functional Theory Studies of Electronic Structures and Hyperfine Interactions of Muonium in Imidazole

2015 ◽  
Vol 749 ◽  
pp. 134-138 ◽  
Author(s):  
Pek Lan Toh ◽  
Shukri Sulaiman ◽  
Mohamed Ismail Mohamed Ibrahim ◽  
Lee Sin Ang
Keyword(s):  
Density Functional Theory ◽  
Electronic Structures ◽  
Density Functional ◽  
Hyperfine Interactions ◽  
Geometry Optimization ◽  
Optimization Procedure ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Total Energies ◽  
Structure Calculations

We carried out ab initio electronic structure calculations in the frameworks of the Density Functional Theory (DFT) to study the electronic structures and hyperfine interaction of muonium (Mu) in imidazole (C3H4N2) and 1–methylimidazole (CH3C3H3N2). The local energy minima and hyperfine interactions of the Mu trapped at the three studies sites were determined by performing geometry optimization procedure. The results show the total energies for all three studied sites are close to one another. The Mu hyperfine interactions were also determined, with the corresponding values vary from 343.00 MHz to 471.28 MHz for the imidazole–Mu cluster, and from 380.21 MHz – 465.57 MHz to 475.93 MHz for the cluster of 1–methylimidazole–Mu, respectively.

Calculation of electronic structure and mechanical properties of DO3–Fe75-xSi25Nix intermetallic compounds by first principles

2015 ◽  
Vol 29 (13) ◽  
pp. 1550087
Author(s):  
R. Ma ◽  
M. P. Wan ◽  
J. Huang ◽  
Q. Xie
Keyword(s):  
Mechanical Properties ◽  
Intermetallic Compounds ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Elastic Parameters ◽  
Functional Theory ◽  
Ni Content ◽  
The Density Functional Theory ◽  
The Difference

Based on the density functional theory (DFT), the plane-wave pseudopotential method was used to investigate the electronic structures and mechanical properties of DO 3– Fe 75-x Si 25 Ni x(x = 0, 3.125, 6.25 and 9.375) intermetallic compounds. The elastic parameters were calculated, and then the bulk modulus, shear modulus and elastic modulus were derived. The paper then focuses on the discussion of ductility and plasticity. The results show that by adding appropriate Ni to Fe 3 Si intermetallic compound can improve the ductility. But the hardness will increase when the Ni content exceeds 6.25%. Analysis of density of states (DOS) and overlap populations indicates that with the difference of the strength of bonding and activity, there were some differences of ductility among different Ni contents. The Fe 71.875 Ni 3.125 Si 25 has the lowest hardness because the covalent bonding (Fe–Si bond and Si–Ni bond) has the minimum covalent electrons.

First-principles study of the structural and elastic properties of Ti5Si3 with substitutions Zr, V, Nb, and Cr

2010 ◽  
Vol 25 (12) ◽  
pp. 2317-2324 ◽  
Author(s):  
Hui-Yuan Wang ◽  
Wen-Ping Si ◽  
Shi-Long Li ◽  
Nan Zhang ◽  
Qi-Chuan Jiang
Keyword(s):  
Density Functional Theory ◽  
Elastic Properties ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Elastic Moduli ◽  
Site Occupancy ◽  
Formation Enthalpy ◽  
Functional Theory ◽  
The Density Functional Theory

The formation enthalpy, electronic structures, and elastic moduli of the intermetallic compound Ti5Si3 with substitutions Zr, V, Nb, and Cr are investigated by using first-principles methods based on the density-functional theory. Our calculation shows that the site occupancy behaviors of alloying elements in Ti5Si3, determined by their atom radius, are consistent with the available experimental observations. Furthermore, using the Voigt–Reuss–Hill (VRH) approximation method, we obtained the bulk modulus B, shear modulus G, and the Young’s modulus E. Among these four substitutions, the V, Nb, and Cr substitutions can improve the ductility of Ti5Si3 effectively, while Zr substitution has little effect on the elastic properties of Ti5Si3. The elastic property variations of Ti5Si3 due to different substitutions are found to be correlated with the Me4d–Me4d antibonding and the strengthened Me4d–Si bonding in the solids.

The Structure and Stability of C20 Dimer

2015 ◽  
Vol 1096 ◽  
pp. 228-231
Author(s):  
Ting Ting Dai ◽  
Pei Ying Huo ◽  
Ji Cai Yu ◽  
Huan Liu ◽  
Yan Xia Song ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Ground State ◽  
Electronic Structures ◽  
Density Functional ◽  
Ground State Structure ◽  
State Structure ◽  
Carbon Cage ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
The Stability

The possible geometrical and electronic structures of C20dimer are optimized by using the density functional theory at B3LYP/LANL2DZ level, stable structure of C20dimer are obtained. The stability of the ground state structure have been studied. The results showed that: there was a slight expansion in carbon cage of C20 dimer ; its chemical stability and thermal stability have been improved.

Computational insights into the photophysical and electroluminescence properties of homoleptic fac-Ir(C^N)3 complexes employing different phenyl-derivative-featuring phenylimidazole-based ligands for promising phosphors in OLEDs

2016 ◽  
Vol 45 (7) ◽  
pp. 3034-3047 ◽  
Author(s):  
Jieqiong Li ◽  
Li Wang ◽  
Kenan Sun ◽  
Jinglai Zhang
Keyword(s):  
Density Functional Theory ◽  
Electronic Structures ◽  
Density Functional ◽  
Photophysical Properties ◽  
Density Functional Theory Method ◽  
Theory Method ◽  
Functional Theory ◽  
Phenyl Derivative ◽  
The Density Functional Theory

The electronic structures and photophysical properties of three homoleptic iridium(iii) complexes IrL3 with C^N ligands are investigated by means of the density functional theory method.

First-Principle Study of Electronic Structures of Y-Doped Mg2Si

2011 ◽  
Vol 689 ◽  
pp. 102-107 ◽  
Author(s):  
Wen Hao Fan ◽  
Rui Xue Chen ◽  
Pei De Han ◽  
Qing Sen Meng
Keyword(s):  
Electronic Structure ◽  
Electronic Structures ◽  
Density Functional ◽  
Energy Structure ◽  
First Principle ◽  
Functional Theory ◽  
Structure Relaxation ◽  
Substitution Site ◽  
The Density Functional Theory ◽  
Correlation Potential

The formation energy, structure relaxation and electronic structure of Mg2Si and Y-doped Mg2Si are investigated using first-principle calculations based the density functional theory. The general gradient approximation was used to treat the exchange and correlation potential. The calculated electronic structure shows that Mg2Si is a semiconductor with a direct gap of 0.27eV at G point. The preferential substitution site of Y inside Mg2Si is determined to be Mg. Y-doping makes the Si atoms around the impurity outward relaxation and increases the Seebeck coefficient, electrical conductivity and thermal conductivity of Mg2Si crystals simultaneously.

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