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1

Electronic structure, stability, and strength of Cu-NiAl alloys : experiment and DFT investigation

Zarhri Zakaryaa

Opto-Electronics Review

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2022

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Vol. 30, No. 2

art. no. e141707

EN

In this study, the copper doping effect on the NiAl structural stability, strength, and electronic structure was investigated. The samples were prepared using induction melting at 2073 K. This material presents good mechanical and physical properties such as high-temperature strength, fatigue or impact, and corrosion resistance which meet technical requirements of many applications. The microstructure of the Cu-doped nickel aluminide was studied using a metallurgical microscope and its lattice parameter was also studied and characterized using an X-ray diffractometer for different concentrations of Cu. The lattice constant of the existing phases was calculated, and it was found that the lattice distortion and gamma prime phase energy have high values allowing the increase of the entropy term of the alloy and subsequently increasing its hardness. From the ab-initio calculation, it was determined that the Cu atoms have the Al sites as a preferred site and prefer to bond with Ni atoms which leads to the improvement of the material hardness. Ab-initio density functional theory was applied to study the formation energy that revealed increasing with Cu amount.

2

Progowa spektroskopia fotoelektronowa cząsteczek

Zubek Mariusz

Postępy Fizyki

|

2021

|

T. 72, z. 2

2--8

PL

Spektroskopia fotoelektronowa stosowana jest w badaniach struktury i dynamiki zewnętrznych i wewnętrznych powłok elektronowych atomów, cząsteczek oraz klasterów w fazie gazowej. W artykule przedstawiono progową spektroskopię fotoelektronową, w której rejestruje się fotoelektrony z prawie zerową energią kinetyczną. Zilustrowano ją omawiając progowe widma fotoelektronowe cząsteczek azotu i furanu otrzymane w pomiarach z wykorzystaniem promieniowania synchrotronowego. Widma te wskazują na znaczny udział stanów autojonizacyjnych w procesach fotojonizacji progowej.

EN

Photoelectron spectroscopy is applied to investigate electronic structure and electron dynamics in outer and inner shells of atoms, molecules and clusters in the gas phase. he article presents threshold photoelectron spectroscopy is presented, in which photoelectrons with near zero kinetic energy are detected. It is illustrated by describing the photoelectron spectra of nitrogen and furan obtained in the measurements using synchrotron radiation. These spectra show signifcant contributions of the autoionizing states to the processes of threshold photoionization.

3

Charakterystyka struktury elektronowej heteropolikwasu fosforowolframowego H3PW12O40 modyfikowanego kationem Fe2+

Niemiec Piotr Jan

Science, Technology and Innovation

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2020

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Vol. 11, no. 4

24--32

PL

W pracy zbadano wpływ podstawienia atomu wolframu atomem żelaza w pierwszorzędowej strukturze heteropolikwasu fosforowolframowego o budowie anionu Keggina. Charakterystykę struktury elektronową zmodyfikowanego heteropolikwasu przeprowadzono za pomocą: analizy populacyjnej NBO, całkowitych (PDOS) i parcjalnych (PDOS) widm gęstości stanów, energetyki i charakteru chemicznego orbitali granicznych (HOMO/LUMO) oraz rozmiaru przerwy wzbronionej (gap). Dodatkowo zbadano mechanizm oddziaływania modyfikowanego kationem Fe2+ heteropolikwasu fosforowolframowego z cząsteczką H2O pełniącą rolę środowiska reakcji chemicznej. W większości charakterystyk stwierdzono istotny wpływ wprowadzonego metalu przejściowego na ww. właściwości w stosunku do heteropolikwasu wyjściowego H3PW12O40.

EN

In this paper the influence of substituting the tungsten atom with an iron ion in the primary structure of the phosphotungstic heteropolyacid with the Keggin anion structure was investigated. Characterization of the electronic structure of the modified heteropolyacid was performed using: population analysis according to NBO scheme, total (TDOS) and partial (PDOS) density of states spectra, energy and chemical character of frontier orbitals (HOMO/LUMO) and the size of the HOMO-LUMO band gap. Additionally, the mechanism of interaction between the Fe2+ with H2O molecule, acting as a chemical reaction medium, was investigated. Most cases showed a significant effect of the introduced transition metal ion (Fe2+) on the above-mentioned properties in relation to the nonmodified heteropolyacid H3PW12O40.

4

First-principles calculations of electronic structure of rhodochrosite with impurity

He Guichun, Li Kun, Li Kun, Guo Tengbo, Li Shaoping, Huang Chaojun, Zeng Qinghua

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 1

195--203

EN

The electronic structure of rhodochrosite containing impurity defects is studied by using the first principles density functional theory. The energy band structure, density of states and electronic distribution are calculated for rhodochrosite crystal models with various impurities (e.g., Cu, Ca, Mg, Zn, Fe). This paper discusses the effects of such defects on the electronic structure of rhodochrosite. The calculation results show that the impurity defects have a great impact on the surface electrical properties of rhodochrosite. For example, Ca and Mg impurities reduce the semiconductor width of rhodochrosite. Both Ca and Mg atoms in orbital bonding act as electron donors in which Ca3p and Mg2p orbits provide electrons while O2p orbits receive electrons. Moreover, the more number of valence electrons of Mn is the weaker covalent interaction between Mn and O atoms will be. Meanwhile, decrease of the total energy of rhodochrosite, makes the structure more stable. When Fe, Zn and Cu impurities are contained, the forbidden gap becomes narrower, which improves the conductivity of rhodochrosite. In addition, impurity bands will be formed in the 3d orbits of rhodochrosite as shown in its density of states, and the number of electrons in 3d orbits will increase. This weakens the covalence of O atoms, decreases the population values of O-Mn, increases the bond length, and enhances the ionicity of O-Mn bonds. The impurity of all defects considered in this study have shown an improved conductivity of rhodochrosite, and increased hole concentration of Mn atoms, which will be of great benefit to the adsorption of anionic collectors and enhance the electrochemical properties for rhodochrosite flotation process.

5

First-principles calculations to investigate structural, electronic and optical properties of (AlSb)m/(GaSb)n superlattices

Caid M., Rached D.

Materials Science Poland

|

2020

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Vol. 38, No. 2

320--327

EN

The structural, electronic and optical properties of (AlSb)m/(GaSb)n (m-n: 1-1, 2-2, 1-3 and 3-1) superlattices are investigated within the density functional theory (DFT) by using the last version of the first principles full potential linear muffin tin orbital method (FP-LMTO) as implemented in LmtART 7.0 code. The exchange and correlation potential is treated by the local density approximation (LDA) for the total energy calculations. Our calculations of the band structure show that the superlattices (n ≠ 1) have a direct band gap Γ-Γ. The optical constants, including the dielectric function ϵ(w), the refractive index n(w) and the reflectivity R(w) are calculated and discussed.

6

Enhancement of electronic, photophysical and optical properties of 5,5′-Dibromo-2,2′-bithiophene molecule : new aspect to molecular design

Muz İ., Kurban M.

Opto-Electronics Review

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2019

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Vol. 27, No. 2

113--118

EN

The aims of this study were to enhance electronic, photophysical and optical properties of molecular semiconductors. For this purpose, the isomers of the B-doped molecule (5,5′-Dibromo-2,2′-bithiophene) have been investigated by density functional theory (DFT) based on B3LYP/6-311++G** level of theory. The isomers were first calculated using kick algorithm. The most stable isomers of the B-doped molecule are presented depending on the binding energy, fragmentation energy, ionization potential, electron affinity, chemical hardness, refractive index, radial distribution function and HOMO-LUMO energy gap based on DFT. Ultraviolet-visible (UV–vis) spectra have been also researched by time-dependent (TD) DFT calculations. The value of a band gap for isomer with the lowest total energy decreases from 4.20 to 3.47 eV while the maximum peaks of the absorbance and emission increase from 292 to 324 nm and 392 to 440 nm with boron doped into 5,5′-Dibromo-2,2′-bithiophene. Obtained results reveal that the B-doped molecule has more desirable optoelectronic properties than the pure molecule.

7

DFT study of optoelectronic spectra of barium cadmium chalcogenides (Ba2CdX3, X = S, Se and Te)

Kumar Sachin, Kumar Naven, Yadav Kamna, Annveer, Singh R. P.

Materials Science Poland

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2019

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Vol. 37, No. 3

417--425

EN

DFT analyses of electronic and optical spectra of barium cadmium chalcogenides (Ba2CdX3, X = S, Se, Te) have been carried out. The study of electronic spectra has been made in terms of band structure and density of states using full potential linear augmented plane wave plus local orbital method. Band structure calculations have been carried out under the approximations PBE-GGA, PBE-Sol, LDA and TB-mBJ. Band structures of these materials show that Ba2CdS3, Ba2CdSe3 and Ba2CdTe3 crystals possess a band gap less than 1 eV, underestimated relative to the experimental/theoretical literature values. Optical spectra of these chalcogenides have been analyzed in terms of real and imaginary parts of dielectric function, reflectivity, refractive index, extinction coefficient, absorption coefficient, optical conductivity and electron energy loss. Optical results show large anisotropy along different directions. These results provide a physical basis of barium cadmium chalcogenides for potential application in optoelectronic devices.

8

Effect of sintering parameters using the central composite design method, electronic structure and physical properties of yttria-partially stabilized ZrO2 commercial ceramics

Mendes A. M., Costa M. C. B., Araújo V. D., Motta F. V., Paskocimas C. A., Acchar W., Longo E., Bomio M. R. D., Cavalcante L. S.

Materials Science Poland

|

2017

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Vol. 35, No. 1

225--238

EN

In this work, the effect of sintering parameters on electronic structure and physical properties of yttria-partially stabilized ZrO2 (YPSZ) commercial ceramics has been studied using the central composite design (CCD) method. The CCD method allows using empirical modelling with better fitting, by considering the interaction between both factors. Different temperature ranges and sintering times for processing of YPSZ ceramics have been used in order to evaluate the grain growth, hardness and volumetric shrinkage by the CCD method. X-ray diffraction patterns and Rietveld refinement data indicate that non-sintered YPSZ ceramics exhibits two phases related to tetragonal and monoclinic structures, while the sintered YPSZ ceramics exhibits a single phase related to a tetragonal structure. Moreover, the monoclinic structure presents zirconium (Zr) atoms coordinated to seven oxygen (O) atoms, while in the tetragonal structure Zr atoms are coordinated to eight O atoms. Field emission scanning electron microscopy images were employed to monitor the sintering and growth process. In addition, the response surfaces obtained from calculations presented the effect of thermal and kinetic variables on the physical properties such as average grain size, volumetric shrinkage and hardness of YPSZ ceramics.

9

Band electronic structure and dielectric functions of (C3N2H5)2SbF5 crystals

Andriyevsky B., Czapla Z.

Zeszyty Naukowe Wydziału Elektroniki i Informatyki Politechniki Koszalińskiej

|

2016

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Nr 10

51--60

EN

Structural and electronic properties of the ferroelastic crystal (C3N2H5)2SbF5 of the molecular type were studied by ab initio methods in the framework of the density functional theory. Band electronic structure, density of electronic states and dielectric functions in the range of valence electrons excitations of the crystal in the monoclinic phase (space group no. 11) have been obtained using the plane waves, ultrasoft pseudopotentials and van-der-Waals corrections. The electronic values obtained are discussed from the viewpoint of the layer-type crystal structure of (C3N2H5)2SbF5.

PL

Strukturalne i elektronowe właściwości ferroelektrycznego kryształu (C3N2H5)2SbF5 typu molekularnego zostały obliczone w ramach teorii funkcjonału gęstości (DFT) z wykorzystaniem odpowiedniej metody z pierwszych zasad (ab initio). Pasmowa struktura elektronowa, gęstość stanów elektronowych i funkcje dielektryczne w zakresie wzbudzenia elektronów walencyjnych kryształu zostały obliczone dla strukturalnej fazy jednoskośnej (grupa przestrzenna no. 11) z wykorzystaniem płaskich fal, super pseudopotencjałów miękkich i uwzględnienia poprawek na oddziaływania międzyatomowe typu van-der-Waalsa. Otrzymane wielkości elektronowe zostały omówione pod kątem warstwowej struktury krystalicznej (C3N2H5)2SbF5.

10

Carbon nanotubes functionalized by salts containing stereogenic heteroatoms as electrodes in their battery cells

Zdanowska S., Pyzalska M., Drabowicz J., Kulawik D., Pavlyuk V., Girek T., Ciesielski W.

Polish Journal of Chemical Technology

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2016

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Vol. 18, nr 4

22--26

EN

This paper concentrates on electrochemical properties of groups of multi-walled carbon nanotubes (MWCNT) functionalized with substituents containing a stereogenic heteroatom bonded covalently to the surface of the carbon nanotube. This system was tested in Swagelok-type cells. The cells comprised a system (functionalized CNT with salts containing S and P atoms) with a working electrode, microfiber separators soaked with electrolyte solution, and a lithium foil counter/reference (commercial LiCoO2 ) electrode. The electrolyte solution was 1 M LiPF6 in propylene carbonate. Using standard techniques (cyclic voltammetry/chronopotentiometry), galvanostatic cycling was performed on the cells at room temperature with a CH Instruments Model 600E potentiostat/galvanostat electrochemical measurements. Methods of functionalization CNT were compared in terms of the electrochemical properties of the studied systems. In all systems, the process of charge/discharge was observed.

11

Structural stability, electronic structure and magnetic properties of the new hypothetical half-metallic ferromagnetic full-Heusler alloy CoNiMnSi

Elahmar M. H., Rached H., Rached D., Benalia S., Khenata R., Biskri Z. E., Bin Omran S.

Materials Science Poland

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2016

|

Vol. 34, No. 1

85--93

EN

We investigated the structural stability as well as the mechanical, electronic and magnetic properties of the Full-Heusler alloy CoNiMnSi using the full-potential linearized augmented plane wave (FP-LAPW) method. Two generalized gradient approximations (GGA and GGA + U) were used to treat the exchange-correlation energy functional. The ground state properties of CoNiMnSi including the lattice parameter and bulk modulus were calculated. The elastic constants (C-ij) and their related elastic moduli as well as the thermodynamic properties for CoNiMnSi have been calculated for the first time. The existence of half-metallic ferromagnetism (HM-FM) in this material is apparent from its band structure. Our results classify CoNiMnSi as a new HM-FM material with high spin polarization suitable for spintronic applications.

12

Structural properties of hypothetical CeBa2Cu3O7 compound from LSDA+DMFT calculations

Łuszczek M.

Materials Science Poland

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2016

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Vol. 34, No. 3

617--626

EN

The hypothetical stoichiometric CeBa2Cu3O7 (Ce123) compound, which has not been synthesized as a single phase yet, was studied by the density functional theory (DFT). We utilized a method which merges the local spin density approximation (LSDA) with the dynamical mean-field theory (DMFT) to account for the electronic correlations. The LSDA+DMFT calculations were performed in the high-temperature range. The particular emphasis was put on the pressure-induced changes in the electronic band structure related to strongly correlated 4f states. The computational results indicate the occurrence of a large negative volumetric thermal expansion coefficient near T = 500 K and a trace of a low-volume isostructural metastable state at high temperatures.

13

Site preference and electronic structure of Mn2RhZ (Z = Al, Ga, In, Si, Ge, Sn, Sb): a theoretical study

Ren Z., Liu Y., Li S., Zhang X., Liu H.

Materials Science Poland

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2016

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Vol. 34, No. 2

251--259

EN

The electronic structure and magnetism of Mn₂RhZ (Z = Al, Ga, In, Si, Ge, Sn, Sb) Heusler alloys have been studied by using first-principles calculations. Three half-metallic ferromagnets, namely, Mn₂RhAl, Mn₂RhGe and Mn₂RhSb have been considered. The calculated equilibrium lattice constant increases with increasing atomic number of Z atoms lying in same column of periodic table. The calculated total magnetic moments M are 2 μ_B/f.u. for Mn₂RhAl and Mn₂RhGa, 3 μ_B/f.u. for Mn₂RhSi, Mn₂RhGe and Mn₂RhSn, and 4 μ_B/f.u. for Mn₂RhSb, which agrees with the Slater-Pauling curve quite well. In all these compounds, except for Mn₂RhSb, the moments of Mn (A) and Mn (B) are antiparallel to each other. The total magnetic moments of the three considered half-metals assume integral values in a wide range of equilibrium lattice parameters.

14

Electronic structure and optical properties of (BeTe)(n)/(ZnSe)(m) superlattices

Caid M., Rached H., Rached D., Khenata R., Bin Omran S., Vashney D., Abidri B., Benkhettou N., Chahed A., Benhellal O.

Materials Science Poland

|

2016

|

Vol. 34, No. 1

115--125

EN

The structural, electronic and optical properties of (BeTe)n/(ZnSe) m superlattices have been computationally evaluated for different conﬁgurations with m = n and m≠n using the full-potential linear mufﬁn-tin method. The exchange and correlation potentials are treated by the local density approximation (LDA). The ground state properties of (BeTe)n/(ZnSe) m binary compounds are determined and compared with the available data. It is found that the superlattice band gaps vary depending on the layers used. The optical constants, including the dielectric function ε(ω), the refractive index n(ω) and the refractivity R(ω), are calculated for radiation energies up to 35 eV.

15

Electronic and optical properties of Mn–S co-doped anatase TiO2 from first-principles calculations

Wu G., Zheng S. K., Yan X.

Materials Science Poland

|

2016

|

Vol. 34, No. 1

38--44

EN

The electronic and optical properties of Mn–S co-doped anatase TiO2 were calculated using the plane-wave-based ultrasoft pseudopotential density functional method within its generalized gradient approximation (GGA). The calculated results show that the band gap of Mn–S co-doped TiO2 is larger than that of the pure TiO2, and two impurity bands appear in the forbidden band, one of which above the valence band plays a vital role for the improvement of the visible light catalytic activity. The Mn–S co-doped anatase TiO2 could be a potential candidate for a photo catalyst because of its enhanced absorption ability of visible light.

16

Ab Initio Study of Structure, Electronic and Magnetic Properties of YFe5 Phase Compound in the DFT Formalism

Gruszka K., Nabiałek M., Noga T

Archives of Metallurgy and Materials

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2016

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Vol. 61, iss. 1

369--374

EN

Paper presents results of studies on structural, electronic and magnetic properties of YFe5 compound using density functional theory (DFT) approach. The GGA functional with ultrasoft pseudopotentials were used as implemented in Quantum Espresso software. The structure of YFe5 compound was examined in three different states namely nonmagnetic, antiferromagnetic and ferromagnetic. Also two antiferromagnetic configurations were considered. From the total energy viewpoint the most likely ferromagnetic configuration is favorable. In order to achieve mentioned aims we present projected density of states, electronic band structure and Löwdin population analysis studies results.

17

Mössbauer study of a tetrakis (pentafl uorophenyl) porphyrin iron (III) chloride in comparison with the fluorine unsubstituted analogue

Kaczmarzyk T., Dziedzic-Kocurek K., Rutkowska I., Dziliński K.

Nukleonika

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2015

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Vol. 60, No. 1

57--61

EN

Mössbauer investigations, in association with density functional theory (DFT) calculations, have been conducted for the molecular and electronic structures of iron (III) [tetrakis (pentafl uorophenyl)] porphyrin chloride [(F20TPP)Fe:Cl], as a Fe(III)-tetraphenylporphyrin complex containing chloride axial ligand and substituted hydrogen atoms by fl uorine ones in the four phenyl rings, in comparison with its fl uorine unsubstituted analogue [(TPP)Fe:Cl]. It was found that the parameters of Mössbauer spectra of both complexes are close to one another, and correspond to the high-spin state of Fe(III) ions, but they show the different temperature dependence and the quadrupole doublets in Mössbauer spectra show different asymmetry at low temperatures. Results of DFT calculations are analyzed in the light of catalytic activity of the halogenated complex.

18

Mössbauer spectroscopy of reduced forms of a Fe-tetraphenylporphyrine complex

Kaczmarzyk T., Rutkowska I., Dziliński K.

Nukleonika

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2015

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Vol. 60, No. 1

51--55

EN

Molecular and electronic structure changes during successive reduction of a Fe-tetraphenylporphyrin chloride [Fe(III)(TPP):Cl] complex are reported on the basis of Mössbauer spectroscopy and DFT calculations. It is established that the attachment of additional electrons to a neutral Fe(III)(TPP):Cl molecule leads to signifi cant shortening of Fe-N distances at the fi rst stage of the reduction Fe(III)(TPP):Cl →Fe(II)(TPP) and lengthening of these bonds at the second stage Fe(II)(TPP)→Fe(I)(TPP). Changes of other bond lengths of the porphyrin ring also appear but in less degree. Interaction of Fe(II) and Fe(I)(TPP) with tetrahydrofuran (THF) solvent is considered. Electron configuration of Fe(II)(TPP) corresponds to intermediate-spin (S = 1) state and in the case of Fe(I)(TPP) low-spin state (S = ½) is observed. Electron density distribution in Fe(II)- and Fe(I)(TPP) complexes, in association with Mössbauer data, is analyzed. Good correlation between experimental and theoretical results was obtained.

19

First principles study of structure, electronic and optical properties of Y3Fe5O12 in cubic and trigonal phases

Shen T., Hu C., Dai H., Yang W., Liu H., Wei X.

Materials Science Poland

|

2015

|

Vol. 33, No. 1

169--174

EN

First principles calculations have been performed to investigate the structure, electronic and optical properties of Y3Fe5O12. Both the cubic and trigonal phases have been considered in our calculation. The calculated structural parameters are slightly larger than the experimental values. The band structures show that Y3Fe5O12 in cubic and trigonal phases have direct band gaps of 0.65 and 0.17 eV. The calculations of dielectric function, absorption, extinction coefficient, refractive index, energy loss function and reflectivity are presented.

20

Badanie struktury elektronowej i własności magnetycznych monokryształów związków międzymetalicznych R-T (R - pierwiastek ziem rzadkich, T - metal przejściowy 3d, 4d, 5d)

Talik E.

Zeszyty Historyczne Politechniki Warszawskiej

|

2014

|

z. 16

7--22