Effect of Alloying Elements V, Cr and Ni on the Electronic Structure and Mechanical Properties of FeAl from First-Principles Calculation

The structure stability, mechanical properties and electronic structures of B2 phase FeAl intermetallic compounds and FeAl ternary alloys containing V, Cr or Ni were investigated using first-principles density functional theory calculations. Several models are established. The total energies, cohesive energies, lattice constants, elastic constants, density of states, and the charge densities of Fe8Al8 and Fe8XAl7 ( X=V, Cr, Ni ) are calculated. The stable crystal structures of alloy systems are determined due to the cohesive energy results. The calculated lattice contants of Fe-Al-X ( X= V, Cr, Ni) were found to be related to the atomic radii of the alloy elements. The calculation and analysis of the elastic constants showed that ductility of FeAl alloys was improved by the addition of V, Cr or Ni, the improvement was the highest when Cr was used. The order of the ductility was as follows: Fe8CrAl7 > Fe8NiAl7 > Fe8VAl7 > Fe8Al8. The results of electronic structure analysis showed that FeAl were brittle, mainly due to the orbital hybridization of the s, p and d state electron of Fe and the s and p state electrons of Al, showing typical characteristics of a valence bond. Micro-mechanism for improving ductility of FeAl is that d orbital electron of alloying element is maily involved in hybridization of FeAl, alloying element V, Cr and Ni decrease the directional property in bonding of FeAl.

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A First-Principles Study of the Cu-Containing β″ Precipitates in Al-Mg-Si-Cu Alloy

Materials ◽

10.3390/ma14247879 ◽

2021 ◽

Vol 14 (24) ◽

pp. 7879

Author(s):

Shaozhi He ◽

Jiong Wang ◽

Donglan Zhang ◽

Qing Wu ◽

Yi Kong ◽

...

Keyword(s):

Mechanical Properties ◽

Electronic Structure ◽

First Principles ◽

Density Functional ◽

Electron Interaction ◽

Structure Stability ◽

First Principles Calculations ◽

Functional Theory ◽

Cu Alloy ◽

Work First

The nanostructured β″ precipitates are critical for the strength of Al-Mg-Si-(Cu) aluminum alloys. However, there are still controversial reports about the composition of Cu-containing β″ phases. In this work, first-principles calculations based on density functional theory were used to investigate the composition, mechanical properties, and electronic structure of Cu-containing β″ phases. The results predict that the Cu-containing β″ precipitates with a stoichiometry of Mg4+xAl2−xCuSi4 (x = 0, 1) are energetically favorable. As the concentration of Cu atoms increases, Cu-containing β″ phases with different compositions will appear, such as Mg4AlCu2Si4 and Mg4Cu3Si4. The replacement order of Cu atoms in β″ phases can be summarized as one Si3/Al site → two Si3/Al sites → two Si3/Al sites and one Mg1 site. The calculated elastic constants of the considered β″ phases suggest that they are all mechanically stable, and all β″ phases are ductile. When Cu atoms replace Al atoms at Si3/Al sites in β″ phases, the values of bulk modulus (B), shear modulus (G), and Young’s modulus (E) all increase. The calculation of the phonon spectrum shows that Mg4+xAl2−xCuSi4 (x = 0, 1) are also dynamically stable. The electronic structure analysis shows that the bond between the Si atom and the Cu atom has a covalent like property. The incorporation of the Cu atom enhances the electron interaction between the Mg2 and the Si3 atom so that the Mg2 atom also joins the Si network, which may be one of the reasons why Cu atoms increase the structure stability of the β″ phases.

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Mechanical Properties and Size Effects of ZnO Nanowires Studied by First-Principles Calculation

Materials Science Forum ◽

10.4028/www.scientific.net/msf.654-656.1670 ◽

2010 ◽

Vol 654-656 ◽

pp. 1670-1673

Author(s):

Zhan Jun Gao ◽

You Song Gu ◽

Yue Zhang

Keyword(s):

Mechanical Properties ◽

First Principles ◽

Size Effects ◽

Density Functional ◽

Elastic Moduli ◽

Axial Direction ◽

Zno Nanowires ◽

First Principles Calculation ◽

Different Diameters ◽

Ground State Energies

First-principles density functional calculations were performed to investigate mechanical properties of ZnO nanowires and the size effects. Structural optimizations were performed first, and a series of strains were applied to the nanowires in the axial direction. The ground state energies were calculated and the elastic moduli of ZnO nanowires were obtained from the energy versus strain curves. It is found that the elastic moduli of the ZnO nanowires with three different diameters (1.2, 1.5 and 1.8nm) are 136.3, 138.7 and 138.0 GPa, respectively, and that of bulk ZnO along [0001] direction is 140.1 GPa. The elastic modulus of ZnO nanowire is slightly lower than that of the bulk and it decreases as the diameter decreases. Comparisons to experimental results and theoretical predications are made.

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The Influence of Electronic Structure Modelling and Junction Structure on First-Principles Chiral Induced Spin Selectivity

10.26434/chemrxiv.12497690 ◽

2020 ◽

Author(s):

Martin Sebastian Zöllner ◽

Vladimiro Mujica ◽

Carmen Herrmann

Keyword(s):

Electronic Structure ◽

First Principles ◽

Density Functional ◽

Orbit Coupling ◽

First Principles Calculation ◽

Physical Parameters ◽

Theory Approach ◽

Spin Orbit Coupling ◽

Spin Orbit ◽

Junction Structure

<br>We have carried out a comprehensive study of the influence of electronic structure modeling and junction structure description on the first-principles calculation of the spin polarization in molecular junctions caused by the chiral induced spin selectivity (CISS) effect. We explore the limits and the sensitivity to modelling decisions of a Landauer / Green’s function / density functional theory approach to CISS. We find that although the CISS effect is entirely attributed in the literature to molecular spin filtering, spin-orbit coupling being partially inherited from the metal electrodes plays an important role in our calculations, even though this effect cannot explain the experi- mental conductance results. Also, an important dependence on the specific description of exchange interaction and spin–orbit coupling is manifest in our approach. This is important because the interplay between exchange effects and spin-orbit coupling may play an important role in the description of the junction magnetic response. Our calculations are relevant for the whole field of spin-polarized electron transport and electron transfer because there is still an open discussion in the literature about the detailed underlying mechanism and the magnitude of relevant physical parameters that need to be included to achieve a consistent description of the CISS effect<br>

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Effects of Doped Elements (Si, Cr, W and Nb) on the Stability, Mechanical Properties and Electronic Structures of MoAlB Phase by the First-Principles Calculation

Materials ◽

10.3390/ma13194221 ◽

2020 ◽

Vol 13 (19) ◽

pp. 4221

Author(s):

Yongxin Jian ◽

Zhifu Huang ◽

Yu Wang ◽

Jiandong Xing

Keyword(s):

Mechanical Properties ◽

Chemical Bonding ◽

First Principles ◽

Electronic Structures ◽

Density Functional ◽

Formation Enthalpy ◽

First Principles Calculation ◽

Elemental Doping ◽

The Stability ◽

W Doping

First-principles calculations based on density functional theory (DFT) have been performed to explore the effects of Si, Cr, W, and Nb elements on the stability, mechanical properties, and electronic structures of MoAlB ternary boride. The five crystals, with the formulas of Mo4Al4B4, Mo4Al3SiB4, Mo3CrAl4B4, Mo3WAl4B4, and Mo3NbAl4B4, have been respectively established. All the calculated crystals are thermodynamically stable, according to the negative cohesive energy and formation enthalpy. By the calculation of elastic constants, the mechanical moduli and ductility evolutions of MoAlB with elemental doping can be further estimated, with the aid of B/G and Poisson’s ratios. Si and W doping cannot only enhance the Young’s modulus of MoAlB, but also improve the ductility to some degree. Simultaneously, the elastic moduli of MoAlB are supposed to become more isotropic after Si and W addition. However, Cr and Nb doping plays a negative role in ameliorating the mechanical properties. Through the analysis of electronic structures and chemical bonding, the evolutions of chemical bondings can be disclosed with the addition of dopant. The enhancement of B-B, Al/Si-B, and Al/Si-Mo bondings takes place after Si substitution, and W addition apparently intensifies the bonding with B and Al. In this case, the strengthening of chemical bonding after Si and W doping exactly accounts for the improvement of mechanical properties of MoAlB. Additionally, Si doping can also improve the Debye temperature and melting point of the MoAlB crystal. Overall, Si element is predicted to be the optimized dopant to ameliorate the mechanical properties of MoAlB.

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Electronic structure and optical properties of CsI under high pressure: a first-principles study

RSC Advances ◽

10.1039/c7ra08777b ◽

2017 ◽

Vol 7 (83) ◽

pp. 52449-52455 ◽

Cited By ~ 6

Author(s):

Qiang Zhao ◽

Zheng Zhang ◽

Xiaoping Ouyang

Keyword(s):

Density Functional Theory ◽

High Pressure ◽

Optical Properties ◽

Electronic Structure ◽

First Principles ◽

Calculation Method ◽

Density Functional ◽

First Principles Calculation ◽

Functional Theory ◽

First Principles Study

We investigated the effects of high pressure on the electronic structure and optical properties of a CsI crystal through a first-principles calculation method based on density functional theory.

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Electronic Structure and Ground State Properties of A4[Ag4O4] (A=Na, K and Rb): A First-Principles Study

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.665.43 ◽

2013 ◽

Vol 665 ◽

pp. 43-48

Author(s):

Rajagopalan Umamaheswari ◽

M. Yogeswari ◽

G. Kalpana

Keyword(s):

Electronic Structure ◽

Band Gap ◽

Ground State ◽

First Principles ◽

Density Functional ◽

Electronic Band Structure ◽

First Principles Calculation ◽

Partial Density ◽

Electronic Band ◽

Ground State Properties

The first-principles calculation within density functional theory is used to study in detail the electronic structure and ground state properties of alkali-metal oxoargenates A4[Ag4O4] (A= Na, K and Rb). The total energies calculated within the atomic sphere approximation (ASA) were used to determine the ground state properties such as equilibrium lattice parameter, c/a ratio, bulk modulus and cohesive energy. The theoretically calculated equilibrium lattice constants values are in well agreement with the available experimental values. The electronic band structures, total and partial density of states are calculated. The result of electronic band structure shows that the KAgO and RbAgO are direct band gap semiconductors with their gap lying between the Γ-Γ points, whereas NaAgO is found to be an indirect band gap semiconductor with its gap lying between Z-Γ points.

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First Principles Calculations Study of Lithium-Montmorillonite for Humidity Sensor Application

KnE Engineering ◽

10.18502/keg.v1i1.490 ◽

2016 ◽

Vol 1 ◽

Cited By ~ 1

Author(s):

Triati Dewi Kencana Wungu

Keyword(s):

Electronic Structure ◽

Water Molecule ◽

First Principles ◽

Density Functional ◽

Humidity Sensor ◽

Point Of View ◽

First Principles Calculation ◽

Repulsive Interaction ◽

Hydrogen Atoms ◽

Sensor Application

In this study, we performed calculations on the water molecule adsorbed on lithium montmorillonite using first principles-calculation by means of electronic-structure calculation, with emphasis on approaches based on Density Functional Theory (DFT). The mechanism of water molecule adsorption on the surface of lithium-montmorillonite was investigated from the electronic structure point of view to seek the possibility of using montmorillonite as humidity sensor. The effects of the Van der Waals force to the electronic properties of water molecule on the surface of montmorillonite was also considered and obtained that the structure is more stable energetically. The interaction of water molecule with surface of montmorillonite yields the rotation of the hydrogen atoms of water molecule due to the occurrence of repulsive interaction between two positive ions of hydrogen of water molecule and lithium. From the calculations, lithium-montmorillonite can be considered as a good material for humidity sensor application since there is an electrical change observed even though it is a relatively small that is 0.657 eV.

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First-Principles Study of the Mechanical Properties of Mg-Based Alloys with FCC and Hexagonal Structure

Materials Science Forum ◽

10.4028/www.scientific.net/msf.610-613.848 ◽

2009 ◽

Vol 610-613 ◽

pp. 848-852

Author(s):

Na Wang ◽

Wei Yang Yu ◽

Wei Bing Zhang ◽

Bi Yu Tang ◽

Xiao Qin Zeng ◽

...

Keyword(s):

Mechanical Properties ◽

Single Crystal ◽

Elastic Constants ◽

First Principles ◽

Density Functional ◽

Hexagonal Structure ◽

Experimental Investigations ◽

Generalized Gradient ◽

Functional Theory ◽

Fundamental Mechanism

More and more research has been focused on the improvement of the mechanical properties and the optimal design of the new excellent Mg-based alloys. In spite of many experimental investigations, the theoretical studies of the mechanical properties are very scarce. First-principle calculations of the elastic constants and mechanical properties of typical Mg-based alloys become necessary to understand the fundamental mechanism governing the observed mechanical properties. In this paper, the single-crystal elastic constants Cijs of the typical fcc and hexagonal structured Mg-based alloys (Mg3Zn3Y2 and CaMg2) were calculated, using density functional theory within the generalized gradient approximation. Then the bulk modulus B, shear modulus G, Young’s modulus E, Poisson’s ratio ν and anisotropy value A were derived from single-crystal elastic constants. The mechanical properties such as the ductility and stiffiness of the alloys are analyzed and discussed in comparison with experimental observations.

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The structure, elastic and thermodynamic properties of Ti2GaC from first-principles calculation

International Journal of Modern Physics B ◽

10.1142/s0217979219500309 ◽

2019 ◽

Vol 33 (06) ◽

pp. 1950030 ◽

Cited By ~ 1

Author(s):

Xiao-Xia Pu ◽

Xiao-Jiang Long ◽

Lin Zhang ◽

Jun Zhu

Keyword(s):

Thermodynamic Properties ◽

Elastic Constant ◽

Bulk Modulus ◽

Elastic Constants ◽

First Principles ◽

Density Functional ◽

Mechanical Stability ◽

Theoretical Data ◽

Debye Model ◽

First Principles Calculation

In this work, the structure, elastic and thermodynamic properties of Ti2GaC at high pressure (P) and high-temperature (T) are studied based on the density functional first-principles. The lattice parameters and elastic constants are well consistent with some theoretical data and experimental results. The elastic constant of Ti2GaC increase monotonously with the increase of pressure (P), which demonstrates the mechanical stability of Ti2GaC at the pressure (P) from 0 to 200 GPa. Mechanical properties including Poisson’s ratio ([Formula: see text]), Young’s modulus (E), shear modulus (G) and bulk modulus (B), which are obtained from elastic constants C[Formula: see text]. The ratio B/G value shows that Ti2GaC is a brittle material, but its enhancing ductility significantly with the elevate of pressure (P). The Grüneisen parameters ([Formula: see text]), thermal expansion coefficient ([Formula: see text]), heat capacity (C[Formula: see text]), elastic constant (C[Formula: see text]), bulk modulus (B), energy (E) and volume (V) with the change of temperature (T) or pressure (P) are calculated within the quasi-harmonic Debye model for pressure (P) and temperatures (T) range in 1600 K and 100 GPa. Besides, densities of states and energy band are also obtained and analyzed in comparison with available theoretical data.

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Electronic structure and phase stability of In-free photovoltaic semiconductors, Cu2ZnSnSe4 and Cu2ZnSnS4 by first-principles calculation

MRS Proceedings ◽

10.1557/proc-1165-m04-03 ◽

2009 ◽

Vol 1165 ◽

Cited By ~ 34

Author(s):

Tsuyoshi Maeda ◽

Satoshi Nakamura ◽

Takahiro Wada

Keyword(s):

Electronic Structure ◽

Plane Wave ◽

Phase Stability ◽

First Principles ◽

Density Functional ◽

Formation Enthalpy ◽

First Principles Calculation ◽

Enthalpies Of Formation ◽

Functional Formalism ◽

The Difference

AbstractWe have theoretically evaluated the phase stability and electronic structure of Cu2ZnSnSe4 (CZTSe) and Cu2ZnSnS4 (CZTS). The enthalpies of formation for kesterite, stannite and wurtz-stannite phases of CZTSe and CZTS were calculated using a plane-wave pseudopotential method within the density functional formalism. For CZTSe, the calculated formation enthalpy (ΔH) of the kesterite phase (−312.7 kJ/mol) is a little smaller than that of the stannite phase (−311.3 kJ/mol) and much smaller than that of the wurtz-stannite phase (−305.7 kJ/mol). For CZTS, the ΔH of the kesterite phase (−361.9 kJ/mol) is smaller than that of the stannite phase (−359.9 kJ/mol) and much smaller than that of the wurtz-stannite phase (−354.6 kJ/mol). The difference of ΔH between the kesterite and stannite phases for CZTS is greater than that for CZTSe. This indicates the kesterite phase is more stable than the stannite phase in CZTS compared with CZTSe. The valence band maximums (VBMs) of both the kesterite- and stannite-type CZTSe(CZTS) are antibonding orbitals of Cu 3d and Se 4p (S 3p). The conduction band minimums (CBMs) are antibonding orbitals of Sn 5s and Se 4p (S 3p). The Zn atom does not affect the VBM or the CBM in either CZTSe(CZTS). The theoretical band gap of the kesterite phase calculated with sX-LDA in both CZTSe and CZTS is a little wider than that of the wurtz-stannite phase and much wider than that of the stannite phase.

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