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Substitution mechanism of rare earths at fluorapatite characteristic sites : experimental and computational calculations

Xie Jun

Physicochemical Problems of Mineral Processing

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2023

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Vol. 59, iss. 2

art. no. 163418

EN

Rare earths (REs) containing phosphate rock is a potential REs resource. The unclear occurrence mechanism of REs in phosphorite limits its further development and utilization. Fluorapatite (FAP) is the main REs-bearing target mineral in phosphorite, the microscopic mechanism of REs entering FAP still needs to be further studied from the electronic scale. In this paper, the doping mechanism of REs in FAP was studied by experiment combined with GGA+U calculation. The XRD, SEM, and FT-IR characterization results of hydrothermal synthesis products showed that REs (La, Ce, Nd, and Y) entered FAP crystal, and one of every 20 Ca atoms was replaced by a REs atom. The GGA+U calculation indicated that La-O/F, Ce-O/F, Nd-O/F, and Y-O/F were ionic bonds in general, and the bonding strength of La-O/F, Ce-O/F, Nd-O/F, and Y-O/F increased gradually with atomic number. The substitution difference of La, Ce, Nd, and Y was mainly caused by the gain and loss of electrons in f and d orbitals. The substitution mechanism of REs at the characteristic sites of Fap was studied, which provided a theoretical reference for the selective recovery of REs from phosphorus blocks.

2

Thermodynamic Phase Diagram and Phonon stability, Electronic and Optical Properties of FeVSb: A DFT study

Bagheri A., Boochani A., Masharian S. R., Jafarpour F. H.

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 1

331--338

EN

Mechanical, electronic, thermodynamic phase diagram and optical properties of the FeVSb half-Heusler have been studied based on the density functional theory (DFT) framework. Studies have shown that this structure in the MgAgAs-type phase has static and dynamic mechanical stability with high thermodynamic phase consistency. Electronic calculations showed that this compound is a p-type semiconductor with an indirect energy gap of 0.39 eV. This compound’s optical response occurs in the infrared, visible regions, and at higher energies its dielectric sign is negative. The Plasmon oscillations have occurred in 20 eV, and its refraction index shifts to zero in 18 eV.

3

The Ru Impurity Effect on Electronic, Optical and Thermoelectric Properties of MoS2 Nano-Sheet: a DFT Study

Dezfuli Firouzeh Motamad, Boochani Arash, Parhizgar Sara Sadat, Darabi Elham

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 2

461--468

EN

The electronic, optical and thermoelectric properties of MoS2 nano-sheet in presence of the ru impurity have been calculated by density functional theory framework with generalized gradient approximation. The MoRuS2 nano-sheet electronic structure was changed to the n-type semiconductor by 1.3 eV energy gap. The optical coefficients were shown that the loosing optical energy occurred in the higher ultraviolet region, so this compound is a promising candidate for optical sensing in the infrared and visible range. The thermoelectric behaviors were implied to the good merit parameter in the 100K range and room temperatures and also has high amount of power factor in 600K which made it for power generators applications.

4

Electronic, optical and non-linear optical properties of an N-cyclohexylacrylamide molecule : a potential optoelectronic agent

Tanış E., Çankaya N.

Opto-Electronics Review

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2020

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Vol. 28, No. 4

191--196

EN

In this article, synthesis, electronic and optical properties of an N-cyclohexyl-acrylamide (NCA) molecule are described based on different solvent environments and supported by theoretical calculations. Theoretical calculations have been carried out using a density function theory (DFT). Temperature dependence of the sample electrical resistance has been obtained by a four-point probe technique. Experimental and semitheoretical parameters such as optical density, transmittance, optical band gap, refractive index of the NCA for different solvents were obtained. Both optical values and electrical resistance values have shown that NCA is a semiconductor material. The values of HOMO and LUMO energy levels of the headline molecule indicate that it can be used as the electron transfer material in OLEDs. All results obtained confirm that the NCA is a candidate molecule for OLED and optoelectronic applications.

5

Electronic and optical properties of ternary alloys ZnxCd1−xS, ZnxCd1−xSe, ZnSxSe1−x, MgxZn1−xSe

Benchikh K., Abid H., Benchehima M.

Materials Science Poland

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2017

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Vol. 35, No. 1

32--39

EN

The empirical pseudopotential method (EPM) within the virtual crystal approximation (VCA) is used to calculate the electronic and optical properties of ternary alloys ZnxCd1-xS, ZnxCd1-xSe, ZnSxSe1-x and ZnSxSe1-x. The alloy band structures and energy gaps are calculated using VCA which incorporates the compositional disorder as an effective potential. The calculated band structures for the ZnxCd1-xS, ZnxCd1-xSe, ZnSxSe1-x and ZnSxSe1-x alloys show a direct band gap in the whole range of the concentration except for the ZnSxSe1-x alloy which presents a crossover from the direct gap to the indirect one.Also the dependence of the refractive index on the concentration is calculated for each ternary alloy. This parameter is found to depend nonlinearly on the alloy concentration. A detailed comparison of our results with experimental data and works of other authors has led to a good agreement.

6

Contribution of on-site Coulomb repulsion energy to structural, electronic and magnetic properties of SrCoO3 for different space groups: first-principles study

Muhammady S., Sutjahja I. M.

Materials Science Poland

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2017

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Vol. 35, No. 4

846--856

EN

We report structural, electronic, and magnetic properties of SrCoO3 in Pm3m and P4/mbm space groups, which are calculated by using generalized gradient approximation corrected with on-site Coulomb repulsion U and exchange energies J. The cubic lattice parameter a and local magnetic moments of Co (µCo) are optimized by varying U at Co 3d site. Employing ultrasoft pseudopotential, the values of U = 8 eV and J = 0.75 eV are the best choice for Pm3m space group. We found the value of (µCo) = 2.56 µB, which is consistent with the previous results. It was also found that Co 3d, hybridized with O 2p, is the main contributor to ferromagnetic metallic properties. Besides, norm-conserving pseudopotential promotes a, which is in good agreement with experimental result. However, it is not suitable for P4/mbm space group. By using ultrasoft pseudopotential, the value of U = 3 eV (J = 0.75) is the most suitable for P4/mbm group. Ferromagnetic metallic properties, Jahn-Teller distortion, and reasonable lattice parameters have been obtained. This study shows that U has significant contribution to the calculated properties and also points out that P4/mbm space group with US-PP is suitable to describe experimental results.

7

Quantum chemical studies on the molecular structure, spectroscopic and electronic properties of (6-Methoxy-2-oxo-2H-chromen-4-yl)-methyl pyrrolidine-1-carbodithioate

Evecen M., Tanak H.

Materials Science Poland

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2016

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Vol. 34, No. 4

886--904

EN

In this paper, the molecular geometry, vibrational frequencies and chemical shifts of (6-Methoxy-2-oxo-2H-chromen-4-yl)methyl pyrrolidine-1-carbodithioate in the ground state have been calculated using the Hartree-Fock and density functional methods with the 6-311++G(d,p) basis set. To investigate the nonlinear optical properties of the title compound, the polarizability and the first hyperpolarizability were calculated. The conformational properties of the molecule have been determined by analyzing molecular energy properties. Using the time dependent density functional theory, electronic absorption spectra have been calculated. Frontier molecular orbitals, natural bond orbitals, natural atomic charges and thermodynamical parameters were also investigated by using the density functional theory calculations.

8

First principle calculation of structural, electronic and elastic properties of rare earth nitride

Bhardwaj P., Singh S.

Materials Science Poland

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2016

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Vol. 34, No. 4

715--720

EN

First principle calculation of the electronic and elastic properties of CeN nitride, which crystallizes in the rock-salt structure, is reported in the present paper. The ground state properties, such as lattice constant (a0), bulk modulus (B) and its pressure derivative (B′) are reported. These results show good agreement with the experimental and other theoretical results. Besides, we have studied the Murnaghan’s equation of state, and used it to fit the theoretical electronic ground state energy and obtain thermodynamic quantities such as the bulk modulus. Furthermore the electronic band structure, total density of states and partial density of states of CeN are also discussed.

9

Electronic and structural properties of rare earth pnictides

Bhardwaj R.

Materials Science Poland

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2016

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Vol. 34, No. 1

45--52

EN

In the present paper structural and electronic properties of rare earth pnictides have been presented. The present calculation has been performed using self-consistent tight binding linear muffin tin orbital (TB-LMTO) method within the local density approximation (LDA). The studied compounds undergo a structural phase transition from NaCl-type structure to CsCl-type structure. The electronic band structure and density of states of the pnictides have been reported. The equilibrium lattice parameter a (A), bulk modulus B (GPa), number of f-states at the Fermi level Nf (states/Ry cell) and volume collapse of AmBi and CmBi have also been reported. The calculated equilibrium structural parameters are in good agreement with the available experimental results.

10

Predictive study of structural, electronic, magnetic and thermodynamic properties of XFeO3 (X = Ag, Zr and Ru) multiferroic materials in cubic perovskite structure: first-principles calculations

Moulay N., Ameri M., Azaz Y., Zenati A., Al-Douri Y., Ameri I.

Materials Science Poland

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2015

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Vol. 33, No. 2

402--413

EN

The full potential linear-muffin-tin-orbital method within the spin local density approximation has been used to study the structural, electronic, magnetic and thermodynamic properties of three multiferroic compounds of XFeO3 type. Large values of bulk modulus for these compounds have been obtained, which demonstrates their hardness. The calculated total and partial density of states of these compounds shows a complex of strong hybridized 3d and 4d states at Fermi level. The two degenerate levels e(g) and t(2g) clearly demonstrate the origin of this complex. We have also investigated the effect of pressure, from 0 GPa to 55 GPa, on the magnetic moment per atom and the exchange of magnetic energy between the ferromagnetic and antiferromagnetic states. For more detailed knowledge, we have calculated the thermodynamic properties, and determined heat capacity, Debye temperature, bulk modulus and enthropy at different temperatures and pressures for the three multiferroic compounds. This is the first predictive calculation of all these properties.

11

Investigations of structural, elastic, electronic and thermodynamic properties of lutetium filled skutterudite LuFe4P12 under pressure effect: FP-LMTO method

Boudia K., Ameri M., Al-Douri Y., Ameri I., Bouafia H.

Materials Science Poland

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2015

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Vol. 33, No. 4

867--878

EN

Structural, elastic, electronic and thermodynamic properties of ternary cubic filled skutterudite compound were calculated. We have computed the elastic modulus and its pressure dependence. From the elastic parameter behavior, it is inferred that this compound is elastically stable and ductile in nature. Through the quasi-harmonic Debye model, in which phononic effects are considered, the effect of pressure P (0 to 50 GPa) and temperature T (0 to 3000 degrees C) on the lattice constant, elastic parameters, bulk modulus B, heat capacity, thermal expansion coefficient alpha, internal energy U, entropy S, Debye temperature theta(D), Helmholtz free energy A, and Gibbs free energy G are investigated.

12

First-principles study of atomic structure and electronic properties of Si and F doped anatase TiO2

Li H., Chen L., Liu S., Li C., Meng J., Wang Z.

Materials Science Poland

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2015

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Vol. 33, No. 3

549--554

EN

Chemical doping represents one of the most effective ways in engineering electronic structures of anatase TiO2 for practical applications. Here, we investigate formation energies, geometrical structures, and electronic properties of Si-, F-doped and Si/F co-doped anatase TiO2 by using spin-polarized density functional theory calculation. We find that the co-doped TiO2 is thermodynamically more favorable than the Si- and F-doped TiO2. Structural analysis shows that atomic impurity varies crystal constants slightly. Moreover, all the three doped systems show a pronounced narrowing of band gap by 0.33 eV for the F-doped TiO2, 0.17 eV for the Si-doped TiO2, and 0.28 eV for the Si/F-co-doped TiO2, which could account for the experimentally observed redshift of optical absorption edge. Our calculations suggest that the Si/F-co-doping represents an effective way in tailoring electronic structure and optical properties of anatase TiO2.

13

Theoretical Studies of High-nitrogen-containing Energetic Compounds Based on the s-Tetrazine Unit

Man T. T., Wang K., Zhang J.G., Niu X. Q., Zhang T. L.

Central European Journal of Energetic Materials

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2013

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Vol. 10, no. 2

171-189

EN

In order to develop new high-energy-density materials (HEDMs), we have investigated 12 substituted s-tetrazine (TZ) compounds, where s-tetrazine was substituted by amino, amido and related groups. Density functional theory (DFT) was used to predict the optimized geometries, electronic structures, total energy, heats of formation (HOFs) and densities. In addition the detonation properties were evaluated by using the VLW equation of state (EOS). The standard enthalpy of formation, the Gibbs free energy, entropy and equilibrium constants were used to estimate the success of the synthetic substitution reactions, which provided theoretical support for practical work. The bond dissociation energy (BDE) of bond C-R was calculated at each stage of the substitution reaction. The calculated results showed that substitution of amino, amido and their derivatives in the TZ ring enhances the HOF values and is favorable for increasing the thermal stability. The calculated detonation properties indicated that incorporating the above groups into the TZ ring is benefcial for improving the explosive performance. Considering the detonation properties and thermal stability, the 12 derivatives may be regarded as promising candidates as high-energy-density materials (HEDMs).

14

Struktura i właściwości elektroniczne warstw AIN wytwarzanych w reaktywnym procesie rozpylania magnetronowego

Nowakowska-Langier K., Chodun R., Firek P., Waśkiewicz M., Zdunek K., Szmidt J.

Elektronika : konstrukcje, technologie, zastosowania

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2011

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Vol. 52, nr 11

43-45

PL

W artykule przedstawione zostaly wyniki badań dotyczące struktury i właściwości elektronicznych warstw AIN otrzymywanych w procesie pulsacyjnego reaktywnego rozpylania magnetronowego. Przeprowadzone badania pokazały, że zastosowanie metody rozpylania magnetronowego w układzie "gemini" jest skutecznym sposobem wytworzenia w temperaturze otoczenia (RT) cienkich, transparentnych warstw AIN odznaczających się wystarczającą adhezją do podloży krzemowych. Otrzymywane przez nas warstwy azotku glinu, wzrastające w kierunku <002> odznaczały się nanokrystaliczną strukturą heksagonalnego AIN o parametrze sieci zgodnym z danymi literaturowymi, wartością energetycznej przerwy wzbronionej ok. 5 ... 6 eV oraz wartością napięcia przebicia ok. 3,5...4,4 MV/cm. Z badań autorów wynika, że szczególnie korzystnym zespołem cech strukturalnych oraz właściwości elektronicznych odznaczały się warstwy wytwarzane przy ciśnieniu mieszaniny gazów Ar+N₂, w zakresie 1 ... 2 Pa. Warstwy takie wydają się szczególnie predestynowane do wykorzystania, jako dielektryk bramkowy w strukturze tranzystorów MISFET.

EN

In the present paper we show the results of our investigation concerning a structure and the electrical properties of the AIN layers produced by the non-reactive magnetron sputtering process. Our results show that application of magnetron sputtering in "Gemini" mode allows for effective and room-temperature (RT) deposition on thin, transparent AIN films with good adhesion to Si substrates. Obtained films, growing in <002> crystallographic orientation have nanocrystalline structure of hexagonal AIN with crystallographic parameters staying in agreement with data published so far, the dielectric constant value (εri) equal from 5 to 6.5 and and critical electric field intensity (ΕBR) from 3.6 to 4.4 MV cm⁻¹. The results show that the promising morphology, phase composition and good electrical properties have the films deposited in Ar/N₂, pressure range from 1 to 2 Pa. It makes those deposited material suitable for application in novel microelectronic devices like MISFET transistor.

15

Electronic structures of RCuIn and R2CuIn3 (R = La, Ce, Pr)

Szytuła A, Kalychak Y M, Tyvanchuk Y, Penc B, Winiarski A

Materials Science Poland

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2008

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Vol. 26, No. 4

1061--1067

EN

Electronic structures of ternary compounds RCuIn and R2CuIn3 (R = La, Ce, Pr) have been studied by the X-ray photoelectron spectroscopy. The valence bands and the XPS core levels were investigated. The two families of compounds crystallize in different hexagonal crystal structures: ZrNiAl-type for RCuIn and AlB2-type for R2CuIn3. Analysis of the XPS valence bands indicates that they are mainly determined by the Cu 3d band. The analysis of the Ce 3d spectra based on the Gunnarsson-Schönhammer model gives the hybridization of the 4f electrons with the conduction band equal to 45 meV for CeCuIn and to 140 meV for Ce2CuIn3. The appearance of the 3d94f0 component is a clear evidence of the intermediate valence behaviour for cerium. The 4f occupation number is 0.95 for CeCuIn and 0.92 for Ce2CuIn3. The analysis of the other core levels confirms a small influence of the atomic surrounding on the electronic structure.

16

Influence of the deposition process parameters on electronic properties of BN films obtained by means of RF PACVD

Firek P., Werbowy A., Szmidt J., Kwietniewski M.

Journal of Telecommunications and Information Technology

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2007

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nr 3

33-36

EN

This work presents results of investigations of electronic properties of undoped boron nitride (BN) films produced on Si substrates in the course of radio frequency (rf) PACVD process with boron triethyl (C2H5)3B as the boron source. The influence of the deposition process parameters on thickness and electronic properties (resistivity r, dielectric strength EBR) of BN films based on ellipsometry and I-V curve measurements at room temperature is studied. The obtained results show that proper selection of deposition process parameters allows BN layers with the required thickness and advantageous values of r and EBR to be fabricated. BN becomes therefore an interesting material for microelectronics applications.

17

Cienkie warstwy germanowęglowe otrzymywane w wyładowaniu jarzeniowym - struktura chemiczna.

Szymanowski H.

Inżynieria Materiałowa

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2000

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R. XXI, nr 6

457-459

PL

Badając procesy nakładania w nowym trójelektrodowym reaktorze plazmowym stwierdzono bardzo dużą zależność właściwości otrzymanej warstwy od jednego z parametrów prowadzenia procesu. Wykorzystując różne techniki badawcze poszukiwano odpowiedzi na pytanie: jakie zmiany budowy chemicznej produktu są odpowiedzialne za tak drastyczne zmiany we właściwościach warstwy a-GexCy:H. Dokonano także obliczeń stopnia upakowania warstwy. Na tej podstawie stwierdzono, że zgodnie z teorią stanu amorficznego izolatora, przejście do struktury amorficznego półprzewodnika następuje wówczas, gdy stopień uporządkowania osiągnie odpowiednią wartość krytyczną. Taki typ zmiany właściwości elektronowych nosi nazwę przejścia o charakterze perkolacyjnym.

EN

The new type of reactor for plasma deposition activated by audio frequency electric field was tested for deposition of amorphous hydrogenated films (a-GexCy:H). It was found that small changes of a coupling capacity in the system can cause a step change in the electronic structure of deposited films. Such a change, however, was not manifested by the molecular structure and only monotonic changes of Ge content and cross-linking were observed. The step in the electronic structure was attributed to the amorphous semiconductor-amorphous dielectric transition.