scholarly journals First-principles calculations of magnetic and mechanical properties of Fe-based nanocrystalline alloy Fe80Si10Nb6B2Cu2

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Chong Sun ◽  
Zhengang Shi ◽  
Wenjie Fu ◽  
Linhao Zhang ◽  
Han Li ◽  
...  
Keyword(s):  
Band Structure ◽  
Magnetic Moment ◽  
First Principles ◽  
Density Functional ◽  
Energy Gap ◽  
Population Analysis ◽  
Decisive Role ◽  
Nanocrystalline Alloy ◽  
State Density ◽  
First Principles Calculation

Abstract Based on the first-principles calculation method of density functional theory (DFT), the crystal structure, band structure, magnetic moment, density of state, elastic constant and population analysis of Fe80Si10Nb6B2Cu2 are calculated. The calculation results show that the Fe-based nanocrystalline alloy of this composition has a stable structure, strong resistance to deformation, high hardness and is an alloy with good flexibility. The energy band structure of spin-up and spin-down is basically the same, and the energy gap is 0 eV, showing metallicity. The asymmetry of the electronic state density between the spin-up and spin-down states indicates that the alloy is ferromagnetic, with a magnetic moment of 84.15 μ; the Fe element plays a decisive role in the magnetic properties of this alloy.

Electronic and magnetic properties of bulk and surfaces half-Heusler alloy KCaB and its bulk thermoelectric properties

2021 ◽  
pp. 2150258
Author(s):  
Jabbar M. Khalaf Al-zyadi ◽  
Wed A. Abed ◽  
Ahmed Hamad Ati
Keyword(s):  
Magnetic Moment ◽  
Heusler Alloy ◽  
Density Functional ◽  
Energy Gap ◽  
Relaxation Effect ◽  
First Principles Calculation ◽  
Half Metallic ◽  
Text Type ◽  
Electronic Spin ◽  
Metallic Ferromagnet

This paper discusses the structural, electronic, magnetic, and half-metallic properties of half-Heusler alloy KCaB. First-principles calculation based on density functional theory is successfully used to determine properties at bulk and on the (111) and (001) surfaces of KCaB. KCaB is half-metallic ferromagnet with a magnetic moment of 1 [Formula: see text] and an energy gap equal to 0.82 eV in the lower spin channel. The [Formula: see text]-type doped exhibits higher Seebeck coefficient, electrical conductivity, thermal conductivity, and figure of merit than the [Formula: see text]-type-doped KCaB at room-temperature 300 K. The half-metallic property is preserved in each of the ends Ca and B on the (111) surface and is lost in the ends K (111) and B and KCa (001) slab surface. The relaxation effect on the electronic spin states decreases the magnetic moment of some atoms on the end surface because the relaxation of the atomic sites is affected and the loss of the nearest neighbors affects exchange–correlation interactions. The surface end with Ca is more stable than the surface end with B on the (111) surface and can maintain the property of half metallic under relatively large stress.

First-Principles Calculation of the Optical Properties of Nanocrystalline Silicon

1994 ◽  
Vol 358 ◽  
Author(s):  
Masahiko Hirao
Keyword(s):  
Optical Properties ◽  
Crystallite Size ◽  
First Principles ◽  
Density Functional ◽  
Energy Gap ◽  
Nanocrystalline Silicon ◽  
First Principles Calculation ◽  
Nonradiative Recombination ◽  
Dangling Bonds ◽  
Hydrogen Atoms

ABSTRACTThe electronic structure and optical properties of nanocrystalline silicon were calculated by the first-principles density functional pseudopotential approach. The calculated energy-gap upshift from the bulk-Si value is nearly proportional to the reciprocal of the crystallite size. Dipole transitions across the gap are weakly allowed and the transition elements decrease rapidly with increases in the crystallite size. The apparent lifetime, the time over which the intensity decreases to 1/e of the initial value, decreases sharply from milliseconds to microseconds within a certain temperature range. The effect of dehydrogenation and the structural stability were investigated using an ab initio molecular dynamics technique. When some of the surface hydrogen atoms are removed, subsequent lattice relaxation eliminates dangling bonds. Further dehydrogenation creates mid-gap states due to surface dangling bonds, which act as nonradiative recombination centers. The calculated results are compared with observations of porous Si.

Effects of vacancy on the electronic and optical properties of β-Si3N4 by first-principles

2019 ◽  
Vol 33 (36) ◽  
pp. 1950451
Author(s):  
Xuefeng Lu ◽  
Jianhua Luo ◽  
Panfeng Yang ◽  
Junqiang Ren ◽  
Xin Guo ◽  
...  
Keyword(s):  
Optical Properties ◽  
First Principles ◽  
Density Functional ◽  
Population Analysis ◽  
Perfect Crystal ◽  
Nitrogen Vacancy ◽  
First Principles Calculation ◽  
Electronic And Optical Properties ◽  
Charge Density Difference ◽  
Thermodynamic Conditions

We use a first-principles calculation to explore the effects of vacancies on structural, electronic and optical properties of [Formula: see text]-[Formula: see text] based on density functional theory (DFT). The results show that after optimization, the Si vacancy system of [Formula: see text]-[Formula: see text] is more difficult to produce than N vacancy system under the same thermodynamic conditions. The band gaps including N vacancy and Si vacancy systems are smaller than that of the perfect crystal. The charge density difference and population analysis show that the bonding near Si vacancy has stronger covalent property, whereas those near nitrogen vacancy have stronger ionic property. For Si vacancy system, the materials have much higher values of the imaginary part of the dielectric constant than those of N vacancies and perfect [Formula: see text]-[Formula: see text]. The maximum value of the Si vacancy system in absorption and reflection spectra is lower than those in different nitrogen vacancy systems.

First-principles study on the magnetic properties of IB group transition metal-doped MoS2

2021 ◽  
pp. 2141002
Author(s):  
Duo Wang ◽  
Lu Yang ◽  
Jianan Cao
Keyword(s):  
Magnetic Properties ◽  
Magnetic Moment ◽  
First Principles ◽  
Density Functional ◽  
Defect Formation ◽  
Single Layer ◽  
Energy Difference ◽  
First Principles Calculation ◽  
Orbital Theory ◽  
Impurity Atoms

In this paper, a first-principles calculation method based on density functional theory is used to study the effect of substitutional doping of Au, Ag, and Cu at Mo site on the magnetic properties of the single-layer MoS2 system. It is found that the Au, Ag, and Cu-doped systems can all exhibit ferromagnetic properties at room temperature. The calculation of defect formation energy and hybrid orbital theory confirms that the system can exist stably. After comparing the energy difference, it is concluded that the magnetic properties of the doped system are more stable in the spin-polarized state. The magnetic moment contributed by impurity atoms is limited. The Mo and S atoms near the impurity atoms are induced by the impurity atoms, and the magnetic moment of the system is mainly produced by this method. There is a ferromagnetic coupling between impurity atoms and surrounding Mo atoms.

First-Principles Calculation of the Electronic Structure of SrTiO3

2013 ◽  
Vol 750-752 ◽  
pp. 1199-1202
Author(s):  
Jiang Ni Yun ◽  
Tieen Yin ◽  
Zhi Yong Zhang
Keyword(s):  
Electronic Structure ◽  
Brillouin Zone ◽  
First Principles ◽  
Density Functional ◽  
Population Analysis ◽  
Density Difference ◽  
First Principles Calculation ◽  
Cubic Phase ◽  
High Symmetry ◽  
Electronic Density

The electronic structure, band structure, density of states (DOS) and electronic density difference of paraelectric SrTiO3 in the cubic phase were performed by the first-principles calculation based on the density functional theory (DFT). The energy levels of high symmetry points in the Brillouin zone were listed and Mulliken population analysis was performed for valence bond structures. The top valence band of SrTiO3 is at the R point, and the minimum of the conduction bands is at the Γ point. The calculated value for indirect band gap is 1.84eV in the Brillouin zone. As in other perovskite ABO3 ferroelectrics, the population analysis, DOS and electron density difference show that there is a very strong hybridization between the Ti3d and O2p states in the valence bands, which is responsible for the ferroelectricity tendency.

scholarly journals Exo⇔Endo Isomerism, MEP/DFT, XRD/HSA-Interactions of 2,5-Dimethoxybenzaldehyde: Thermal, 1BNA-Docking, Optical, and TD-DFT Studies

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5970
Author(s):  
Nabil Al-Zaqri ◽  
Mohammed Suleiman ◽  
Anas Al-Ali ◽  
Khaled Alkanad ◽  
Karthik Kumara ◽  
...  
Keyword(s):  
Density Functional ◽  
Energy Gap ◽  
Structural Parameters ◽  
Population Analysis ◽  
Xrd Analysis ◽  
X Ray Diffraction ◽  
Optical Energy Gap ◽  
Functional Theory ◽  
Reactivity Descriptors ◽  
Td Dft

The exo⇔endo isomerization of 2,5-dimethoxybenzaldehyde was theoretically studied by density functional theory (DFT) to examine its favored conformers via sp2–sp2 single rotation. Both isomers were docked against 1BNA DNA to elucidate their binding ability, and the DFT-computed structural parameters results were matched with the X-ray diffraction (XRD) crystallographic parameters. XRD analysis showed that the exo-isomer was structurally favored and was also considered as the kinetically preferred isomer, while several hydrogen-bonding interactions detected in the crystal lattice by XRD were in good agreement with the Hirshfeld surface analysis calculations. The molecular electrostatic potential, Mulliken and natural population analysis charges, frontier molecular orbitals (HOMO/LUMO), and global reactivity descriptors quantum parameters were also determined at the B3LYP/6-311G(d,p) level of theory. The computed electronic calculations, i.e., TD-SCF/DFT, B3LYP-IR, NMR-DB, and GIAO-NMR, were compared to the experimental UV–Vis., optical energy gap, FTIR, and 1H-NMR, respectively. The thermal behavior of 2,5-dimethoxybenzaldehyde was also evaluated in an open atmosphere by a thermogravimetric–derivative thermogravimetric analysis, indicating its stability up to 95 °C.

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.

Pros and cons of time-dependent hybrid density functional approach to optical spectra of solids: a case study of CeO2

2021 ◽  
Author(s):  
Huai-Yang Sun ◽  
Shuo-Xue Li ◽  
Hong Jiang
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Computational Cost ◽  
Optical Spectra ◽  
First Principles Calculation ◽  
Many Body ◽  
Many Body Perturbation Theory ◽  
Pros And Cons ◽  
Hybrid Density Functional

Prediction of optical spectra of complex solids remains a great challenge for first-principles calculation due to the huge computational cost of the state-of-the-art many-body perturbation theory based GW-Bethe Salpeter equation...

scholarly journals Mono- and Bi-Molecular Adsorption of SF6 Decomposition Products on Pt Doped Graphene: A First-Principles Investigation

2018 ◽  
Vol 8 (10) ◽  
pp. 2010 ◽  
Author(s):  
Yongqian Wu ◽  
Shaojian Song ◽  
Dachang Chen ◽  
Xiaoxing Zhang
Keyword(s):  
Single Molecule ◽  
First Principles ◽  
Density Functional ◽  
Energy Gap ◽  
Adsorption Parameters ◽  
Functional Theory ◽  
Decomposition Products ◽  
Before And After ◽  
Doped Graphene ◽  
Sf6 Decomposition

Based on the first-principles of density functional theory, the SF6 decomposition products including single molecule (SO2F2, SOF2, SO2), double homogenous molecules (2SO2F2, 2SOF2, 2SO2) and double hetero molecules (SO2 and SOF2, SO2 and SO2F2, SOF2 and SO2F2) adsorbed on Pt doped graphene were discussed. The adsorption parameters, electron transfer, electronic properties and energy gap was investigated. The adsorption of SO2, SOF2 and SO2F2 on the surface of Pt-doped graphene was a strong chemisorption process. The intensity of chemical interactions between the molecule and the Pt-graphene for the above three molecules was SO2F2 > SOF2 > SO2. The change of energy gap was also studied and according to the value of energy gap, the conductivity of Pt-graphene before and after adsorbing different gas molecules can be evaluated.

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