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1

A first-principle study of the effect of Fe/Al impurity defects on the surface wettability of dolomite

Chen Hong, Ao Xianquan, Cao Yang, Li Cuiqin, Jiang Chunyan

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 4

art. no. 150702

EN

The presence of Fe and Al atoms in large quantities in phosphate ores can significantly affect the surface properties of the minerals during flotation. In this study, the effects of Fe/Al impurities on the adsorption of H2O molecules on dolomite, including the density of states (DOS), Mulliken bond group values, and charge groups, were investigated and the adsorption energy was analyzed using density functional theory. The results show that the adsorption of H2O molecules on perfect and Fe/Al-substituted dolomites is weak chemisorption, and the Fe and Al impurities weaken and enhance the adsorption capacity of H2O molecules, respectively. Therefore, the hydrophilicity of the dolomite surface increases in the following order: Fe-substituted dolomite < perfect dolomite < Al-substituted dolomite. The Mulliken charge and bond group analysis shows that the adsorption of H2O molecules on dolomite is primarily through the interaction between Ow and Ca atoms, where the d orbitals of Ca atoms provide charges for Ow atoms to form ionic bonds, which related to the poor electronegativity of Ca atoms and their weak valence electron binding ability. The DOS analysis shows that, during the adsorption of H2O molecules on dolomite, Mg and Al atoms have less influence on the dolomite surface, whereas Fe and Ca atoms undergo competitive adsorption, which inhibits the interaction between Ca atoms and H2O molecules on the dolomite surface.

2

Mechanisms of electrical conductivity, quantum capacity and negative capacitance effects in InSe (PTHQ) nanohybrid

Ivashchyshyn Fedir, Maksymych Vitaliy, Calus Dariusz, Klapchuk Myroslava, Baryshnikov Glib, Galagan Rostislav, Litvin Valentina, Chabecki Piotr, Bordun Ihor

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2022

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Vol. 70, nr 1

art. no. e139958

EN

In this work, we present findings on the syntheses and study of properties of InSe < PTHQ > nanohybrid. The introduction of guest component in GaSe matrix leads to an increase in inhomogeneities, which is clearly confirmed by the strengthening of the low-frequency horizontal branch of Nyquist diagrams. A constant magnetic field counteracts this effect and changes the behavior of the impedance hodograph at low frequencies to the opposite. Illumination leads to a colossal increase in quantum capacitance, which is clearly demonstrated in the Nyquist diagram. For the synthesized InSe < PTHQ > nanohybrid the interesting behavior of the current-voltage characteristic is reported. As a result of studies of the synthesized InSe < PTHQ > nanohybrid the effect of “negative capacity” is observed, the magnitude of which can be controlled by the electric field. Based on the constructed impedance model and proposed N-barrier model, the physical mechanisms of the investigated processes are suggested.

3

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.

4

Structural determination of Co/TiO2 nanocomposite: XRD technique and simulation analysis

Mostaghni F., Abed Y

Materials Science Poland

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2016

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Vol. 34, No. 3

534--539

EN

Synthesis and complex theoretical and experimental studies of Co/TiO2 anatase have been reported. The preparation of Co/TiO2 was carried out by sol-gel method. Distribution of cations among the two tetrahedral and octahedral sites was estimated by analyzing the powder X-ray diffraction patterns by employing Rietveld refinement technique, and the results revealed the existence of tetragonal structure. Band structure and density of states calculations were performed using the first-principles methods. The structural and electronic properties of Co/TiO2 were calculated in the general gradient approximation (GGA). An additional comparison with pure TiO2 anatase allowed us to clarify cobalt doping effect on the electronic structure and the band gap. The band gap of Co/TiO2 was decreased by broadening the valence band as a result of the overlap among Co 3d, Ti 3d, and O 2p states, which made it respond better to visible and solar light.

5

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.

6

Simulation of optical spectra of novel Tl4CdI6 and Tl4HgI6 optoelectronic crystals

Franiv V, Bovgyra O, Kushnir O, Franiv A, Plucinski K J

Optica Applicata

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2014

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Vol. 44, nr 2

317--326

EN

The results of calculations using local density approximation and generalized gradient approximation: the total energy depending on the volume of the unit cell, the distribution of the total density of states and the partial contributions of electronic orbitals in the band structure of Tl4CdI6 and Tl4HgI6 crystals are shown in this paper. The spectra of the real part of the dielectric permittivity, the spectra of the imaginary part of permittivity, the reflection spectra and the absorption coefficient of both crystals are obtained using the Kramers–Kronig method. A comparative analysis of theoretical calculations with experimental data is carried out. Substantial influence of electron–phonon broadening is shown.

7

The Electronic Properties of New Fe-Based Superconductors

Kruchinin S., Antonchenko V., Zolotovsky A.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2011

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Vol. 15, No 2

203-208

EN

We investigate the band structure of Fe-based superconductors using the first-principle method of density-functional theory. We calculated the band structure and the density of states at the Fermi level for ReFeAsO (Re = Sm, Dy, Ho, Er) superconductors. Our calculations indicate that the maximum critical superconducting transition temperature Tc will be observed for compounds with Sm and Er. We predict that Tc=60K for ErFeAsO.

8

Analityczny model gęstości stanów w strukturze jednowymiarowego kryształu fotonicznego

Rudziński A., Szczepański P., Tyszka-Zawadzka A.

Elektronika : konstrukcje, technologie, zastosowania

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2007

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Vol. 48, nr 7

49-53

PL

Przedstawiono prosty, w pełni analityczny model gęstości stanów w strukturze jednowymiarowego kryształu fotonicznego. Prezentowany model umożliwia analizę wpływu parametrów i defektów kryształu na jego właściwości, dzięki czemu stanowi narzędzie odpowiednie zarówno do badania, jak i projektowania tego typu struktur dla różnych zastosowań. W ogólnej postaci może być on zastosowany do obliczeń dla dowolnych struktur wielowarstwowych.

EN

We present a simple, fully analytical model of density of states in one-dimensional photonic crystal structure. The introduced model allows to investigate the impact of the parameters and defects of the photonic crystal on its properties, thus being a tool adequate for both research and designing of this type of structures for diversified applications. In its general form, the model can be used in calculations for arbitrary multilayer structures.

9

Specific heat related to details of the vibrational modes for a 2D nanocrystalline material

Hahn W.

Materials Science Poland

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2005

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Vol. 23, No. 2

389--399

EN

What - if" analyses of the interfacial component of nanocrystalline materials (NCM), especially at higher temperatures, were performed using a two-dimensional model. What influence would thermal excitations have on the pair distribution function, the vibrational spectra and the specific heat, over the temperature range of 30 - 1200 K, if the NCM would be stable over this temperature range, i.e. if grain growth cannot occur? It turned out that reduction of the grain size and increase in temperature influenced the pair distribution function, the vibrational spectra and specific heats in a similar manner. The changes in the vibrational spectra and the specific heat with decreasing grain size or increasing temperature could be related to changes in the occupation of the vibrational modes. The so-called participation ratio ( PR) proved to be a suitable means of measuring the occupation of the modes and to classify the spectra. The differences in the specific heat could be largely attributed to parts of a subspectrum, filtered out from the complete vibrational spectrum by collecting the modes of a certain participation ratio range.

10

Magnetism of nanocrystalline and bulk fexNi23-xB6 (x=0, 1, 22 and 23) alloys -- experiment and theory

Idzikowski B., Szajek A.

Materials Science

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2003

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Vol. 21, No. 1

73-82

EN

Formation of the nanostructure composed of a metastable magnetically ordered fcc-FexNi23-xB6 phase with large lattice constant (a=1.051-1.082 nm) from amorphous Fe81-y-zNiyZr7B12Auy (y=10-40, 64; z=0, 1) precursors due to the thermal treatment have been studied. Annealing of the y<=20, z=0 samples at temperatures 420-580°C leads to the increase of FexNi23-xB6 fraction embedded in amorphous matrix with grains sizes from few to few dozen nanometres. The structure transformations have been investigated by the DSC, XRD and TEM techniques. Magnetic behaviour of FexNi23-xB6 (x=0, 1, 22 and 23) phases have been studied theoretically using the spin polarized tight binding linear muffintin orbital (TB-LMTO) method. Anomalously high magnetic moments of Fe atoms have been found in some non-equivalent positions in the crystal structure.

11

Coherent potential approximation technique in a simple example of resistivity calculations for binary alloys

Wołoszyn M., Maksymowicz A. Z.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2002

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Vol. 6, No 4

669-680

EN

Technique of the Coherent Potential Approximation applied for calculations of the density of states in binary alloys Ax B(1-x) is presented. Results of the calculations are also used to find the residual resistivity of the system versus concentration x.

12

Quantum chemical studies of Cl-...HNO comlex in the singlet and triplet electronic states

Latajka Z., Ratajczak H.

Bulletin of the Polish Academy of Sciences. Chemistry

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2001

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Vol. 49, No. 2

125-131

EN

The structure and energetics of the hydrogen bonded complex formed between HNO and Cl- in the singlet and triplet states was investigated at the MP2 level with 6-31+ G(d, p) basis set. It is shown that the complex is strongly bound. The binding energy of the complex calculated at the MP4(SDTQ)/6-311++ G(2d,2p) level is -15.42 kcal/mol for the singlet state and —25.75 kcal/mol for the triplet state.

13

Periodic Hartree-Fock studies on (HCl) infinity chain

Berski S., Latajka Z.

Polish Journal of Chemistry

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1998

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Vol. 72, nr 7S

1540-1550

EN

The infinite chain of hydrogen chloride (HCl) infinity is studies by the periodic Hartree-Fock (PHF) method using CRYSTAL 92 program. The basis sets of double zeta type containing sp- diffuse as d-and p- polarization functions are investigated. The relationship between structural and energetic parameters of (HCL) infinity and these basis sets is discussed. Furthermore, it is shown that [12s9p/6s4p] basis set of Veillard and Huzinaga, which was successfully used in stidies on HCl dimer, yields the best geometry of the infinite chain. Based on this basis set, the height of the barier for proton transfer is obtained with value of 39.6 kcal/mol. The comparison of the density of states plots (DOS) computed for (HF) infinity and (HCl) infinity indicates that computational level influences rather slightly the DOS function in case of the hydrogen chloride chain.

14

Carbyne trefoil knots - are they stable enough to exist?

Dobrowolski J.Cz., Mazurek A.P.

Polish Journal of Chemistry

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1998

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Vol. 72, nr 7S

1593-1603

EN

The structure and stability of non-linear carbon clusters of carbyne type was estimated based on ab initio quantum mechanical calculations. Both the cyclic (cacarbynes) and knotted (knocarbynes) trefoil structure of closed polycarbon chains, containing up to 84 carbon atoms, were considered. Comparison of the calculated spectral properties (IR, (13)C NMR) with those of C60 fullerene provide the basis for experimental identification of Cn cyclic and knotted structures as may have implication for interstellar dust spectroscopy.