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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.
EN
Theoretical investigations were performed to study on alloying stability, and electronic structure of (AlCu3, AlCu2Zr and AlZr3). The results show that the lattice parameters obtained after full relaxation of crystalline cells are consistent with experimental data, and these intermetallics have a strong alloying ability and structural stability due to the negative formation energies and the cohesive energies. The further analysis find out that single-crystal elastic constants at zero-pressure satisfy the requirement of mechanical stability for cubic crystals. The calculations on Poisson’s ratio show that AlCu3 is much more anisotropic than the other two intermetallics. In addition, calculations on densities of states indicates that the valence bonds of these intermetallics are attributed to the valence electrons of Cu 3d states for AlCu3, Cu 3d and Zr 4d states for AlCu2Zr, and Al 3s, Zr 5s and 4d states for AlZr3, respectively; in particular, the electronic structure of the AlZr3 shows the strongest hybridization.
PL
Przeprowadzono teoretyczne badania stabilności stopów i struktury elektronowej AlCu3. AlCu2Zr i AlZr3). Obliczania wskazują, że parametry sieci uzyskane po pełnej relaksacji komórek krystalicznych są zgodne z danymi eksperymentalnymi. Związki międzymetaliczne wykazują silną zdolność tworzenia stopów i stabilność strukturalną z powodu ujemnej energii tworzenia i energii spójności. Dalsze analizy wykazały, że stałe elastyczności pojedynczych kryształów przy zerowym ciśnieniu spełniają wymóg stabilności mechanicznej kryształów regularnych. Obliczenia współczynnika Poissona pokazują, że A1Cu3 posiada znacznie bardziej anizotropowe własności niż dwie pozostałe fazy międzymetaliczne. Ponadto, obliczenia gęstości stanów wskazują, że w tworzeniu faz międzymetalicznych biorą udział elektrony walencyjne odpowiednio: Cu na powłoce 3d dla A1Cu3. Cu na 3d i Zr na 4d dla AlCu2Zr. oraz Al na 3s, Zr na 5s i 4d dla AIZr3), w szczególności struktura elektronowa AlZr3) wykazuje najsilniejszą hybrydyzację.
PL
W pracy opisano rezultaty badań teoretycznych struktury elektronowej - wykonanych w oparciu o wyniki obliczeń ab initio, przeprowadzonych za pomocą programu WIEN2k (metoda DFT FP-LAPW stowarzyszonych fal płaskich w pełnym potencjale krystalicznym w ramach formalizmu teorii funkcjonału gęstości) - oraz topologii gęstości elektronowej (w oparciu o formalizm QTAiM kwantowej teorii atomów w cząsteczkach R.F.W. Badera) dla wybranych modelowych roztworów stałych Ag(SbxSn1-x)Se2. Otrzymane wyniki poddane zostały szczegółowej analizie w kontekście wpływu obniżenia lokalnej symetrii i stopnia domieszkowania cyną na kształt i własności struktury elektronowej i topologicznych własności gęstości elektronowej w punktach krytycznych wiązań.
EN
The results of theoretical studies of electronic structure, obtained by means of the full-potential linearized augmented plane wave method within DFT formalism as implemented in Wien2k package, and electron density topology and bonding, obtained by means of the Bader’s quantum theory of atoms in molecules topological analysis of total electron density derived from FP-LAPW calculations, were carried out f orchosen solid solutions of Ag(SbxSn1-x)Se2 and described in the paper. Detailed analysis of the obtained results from the point of view of the dependence of electronic structure and topological properties of bond critical points on local ordering and level of tin doping is presented.
EN
The energetics and electronic structure of the Ca alloying Mg 17Al12 phase have been calculated using a first principles pseudopotential plane-wave method based on the density functional theory. According to the calculation results, the negative heat of formation and the cohesive energy of (Mg17-xCax)Al12 (x = 0. 1, 4, 12) gradually increase when the Mg atoms at the I, II, III positions of the Mg17Al12 phase are substituted with Ca, which indicates that the alloying ability of (Mg17-xCax)A,)Al12 with the replacement of Ca for Mg(III) atoms is the strongest among the three substitutions and (Mg5Ca12)Al12 formed in this manner has the highest structural stability. After comparing the densities of states (DOS) for (Mg17-xCax)Al12 (x = 0. 1, 4, 12), it is found that the increase in the structural stability of Mg 17Al12 alloyed by Ca attributes to an increase in the bonding electron numbers at energy levels below the Fermi level, which mainly originates from the contribution of the valence electron numbers of Al (p) and Ca (s) orbitals.
6
Content available remote Physical properties of polyazomethine thin films doped with iodine
EN
Purpose: The aim of this paper is to show influence of doping 1,4-phenylene-methylenenitrilo-1,4- phenylenenitrilomethylene (PPI) with iodine and to propose doping mechanism and its impact on electronic structure of doped PPI thin films. Design/methodology/approach: Influence of iodine doping on electronic structure of polyazomethine thin films was investigated. Optical absorption spectra, XRD spectra and AFM images of doped PPI thin films were recorded. Findings: Doping mechanism relys on removing one electron from PPI pi-system by 12 molecules and forming counterions 13-. Formation of positive polaron means that doping of polyazomethine PPI is p - type. Research limitations/implications: Influence of iodine doping on electrical properties (with increasing of temperature) of PPI thin layers will be checking with Kethley appliance. We plan these measurements to be done in the foreseeable future. Practical implications: Iodine doping of thin PPI films process could results in better electrical conductivity of PPI, so doped polyazomethine films could find some applications for photonic and optoelectronic devices. Originality/value: Conjugated PPI is rarely enough reported but it is very interesting material as it has nitrogen atom in the backbone and it is isoelectronic counterpart of polyparaphenylenevinylene (PPV). This paper show that doping influences on surface morphology, cristallinity and optical properties of polymer. Furthermore, doping mechanism and changes of polymer electronic structure have been proposed in this paper.
7
Content available remote Konferencja SCTE 2006 [Ze zjazdów i konferencji]
PL
196 uczestników z 23 krajów wzięło udział w kolejnej 15. Międzynarodowej Konferencji "Solid Compounds of Transition Elements", która odbyła się w Krakowie w dniach 15-20 lipca 2006 r. Miejsce to wybrano na poprzedniej konferencji w Linzu w 2003 r. z nadzieją, że umożliwi szersze uczestnictwo naukowcom z krajów środkowo-wschodniej Europy. Tak też się stało. Konferencja miała charakter interdyscyplinarny - skupiła chemików i fizyków ciała stałego oraz specjalistów z zakresu inżynierii materiałowej.
8
Content available remote The electronic and magnetic properties of Nd5Co19B6 and Nd5Co21B4 compounds
EN
The Nd5Co19B6 and Nd5Co21B4 compounds were manufactured as promising systems suitable for fabrication of permanent magnets. They belong to the Rm+nCo5m+3nB2n family having the P6/mmm space group. The band structure calculations are performed by the tight binding version of the linear muffin-tin orbital method in the atomic sphere approximation (TB-LMTO ASA). The calculated magnetic moments on Co atoms depend on their local environment. The calculated values are compared with the bulk measurements.
9
EN
Nanstructured soft magnets are example of materials made by partial crystallization of amorphous precursors. Fe22(Pt,Pd)B6 compounds which crystallize in the Cr23C6-type structure having four inequivalent sites (4a, 8c, 48h, 32f) for Fe, Pd and Pt atoms can form grains of several nanometers in diameter in residual amorphous matrix. Band structure calculations show that the local magnetic moments of Fe atoms depend on their local environments, and for 4a and 8c sites the resultant moments are enhanced up to about 2.5-3 žB/atom. The Pd and Pt atoms prefer location in 4a and 8c positions, respectively. Magnetic moments induced on the substituted atoms are equal to 0.45 žB/atom on Pt atom and 0.39 žB/atom on Pd one.
10
Content available remote Structure and electronic properties of Fe-Ti thin films
EN
Fe/Ti multilayers (MLs) prepared onto glass substrates using UHV RF/DC magnetron sputtering. Results showed a significant drop of the coercivity measured for the Fe/Ti MLs with decrease in Fe layer thickness - typically from Hc ~ 2.2 kA/m to Hc ~ 0.2 kA/m - observed at a critical Fe thickness dcrit ~ 2.3 nm. Structural studies showed that the deposition of the 0.18 nm - Fe / 0.22 nm - Ti ML at 285 K leads to the formation of an uniform amorphous Fe-Ti alloy thin film due to a strong interdiffusion during the growth process. On the other hand, in-situ annealing of this ML at 750 K for 2 h resulted in the creation of a nanocrystalline phase. Furthermore, in-situ XPS studies showed that the valence band of the nanocrystalline Fe-Ti alloy film is broader compared to that measured for the amorphous phase with the same average composition.
EN
In view of a contrasting behaviour of Pd-containing and Rh-containing systems, we investigate solid solutions CeRh1-xPdxAl in order to determine the dependence of their electronic properties on the number of the conduction electrons. We present structural and X-ray photoemission spectroscopy (XPS) data for CeRh1-xPdxAl. We also discuss the influence of the number of free electrons in the conduction band on the stability of the crystallographic structure and the occupation number of the f-shell.
12
Content available remote Electronic structure of the intermetallic rare earth compounds
EN
The electronic structures of intermetallic rare earth compounds of different compositions: RMn2Ge2 (R = Nd, Sm), R3Mn4Sn4 (R = La, Ce, Nd), Ce3Ag4X4 (X = Ge, Sn), and Ce2MnGe6, have been investigated. XPS measurements were performed using a commercial LHS10 spectrometer. The valence band and core-level states have been analysed. In Mn compounds, the Mn 3d state forms a broad band near the Fermi level. The analysis of XPS spectra using the Gunnarsson-Schönhammer model gives the coupling parameters (hybridisation energy) between the R 4f states and electrons of the conduction band
13
Content available remote Electronic structure of f-electron intermetallic compounds studied by positrons
EN
The electronic structure of isostructural rare-earth intermetallic compounds TmGa3, ErGa3, and CeIn3 has recently been studied by measurements of two-dimensional angular correlations of annihilation radiation (2D ACAR) spectra. On the example of these systems we show what kind of information can be exploited from such spectra, i.e. from line projections of the electron-positron (e-p) momentum density ?(p). By applying various tomographic techniques, we check how these algorithms can affect reconstructed 3D momentum densities and Fermi surfaces (FS). We confirm that for all these systems in the paramagnetic phase the f-electrons are fully localized and their FS's are similar. TmGa3 and ErGa3 exhibit the FS nesting feature, in agreement with their magnetic structure, which is not a case in CeIn3.
14
Content available remote Electronic structure of CeRhIn5 and CeIrIn5
EN
We have performed Full Potential Linearized Augmented Plane-Wave (FP-LAPW) calculations of the layered cerium compounds CeRhIn5 and CeIrIn5, which belong to the new, intensively investigated family of heavy fermion (HF) materials. The ground states of this compounds can be tuned between antiferromagnetism (AFM) and superconductivity (SC) by external pressure or doping. We have carried out x-ray photoelectron spectroscopy (XPS) experiments to compare measured valence band spectra with theoretical calculations. We also analyse the XPS 3d Ce spectra, to estimate the occupation of the Ce 4f shell and the hybridization between 4f and conduction electrons. We have found and discussed an influence of the lattice parameter a and the d-f interatomic hybridization effect on the ground state properties in the series of CeMIn5 compounds.
15
Content available remote Electronic structure of Ce2Rh3Al9
EN
We have investigated the XPS spectra of Ce2Rh3Al9 compound and calculated DOS by using the FP-LAPW (Full Potential Linear Augmented Plane Wave) and TB-LMTO-ASA (Tight Binding Linear Muffin Tin Orbitals) methods. The overall agreement between the calculated and the measured XPS valence band spectra is good. Analysis of the 3d XPS (X-ray Photoemission) spectra, using the Gunnarson-Schonhammer theory, suggests a mixed valence behaviour of Ce. FP-LAPW calculations show a half-metallic behaviour of Ce2Rh3Al9, whereas from LMTO calculations results a semiconducting and nonmagnetic ground state. This result is, however, in contradiction to the resistivity (T) experimental observation, which has not shown an activated behaviour. We attribute a possible appearance of the semiconducting/halfmetallic gap for Ce2Rh3Al9 to an atomic disorder.
16
Content available remote Effect of spin-orbit coupling on the electronic structure of bismuthide YbAuBi
EN
The electronic structure of ternary ytterbium YbAuBi and YbAuSn compounds was studied by X-ray photoemission spectroscopy (XPS) and ab-initio methods (LMTO-ASA, FP-LMTO, FPLO). The results showed that the valence bands in these compounds were formed by 4f orbitals of ytterbium and 5d orbitals of transition metals. The full relativistic band calculations (FP LMTO and FPLO) with spin-orbit coupling had shown that 4f peak consisted of two peaks that corresponded to Yb 4f7/2 and 4f5/2 doublet.
17
Content available remote Complex Magnetic Phenomena in f-Electron Intermetallic Compounds
EN
In the paper various aspects of magnetic properties of lanthanide and actinide intermetallic compounds are discussed. The first part deals with 1:2:2: stoichiometry compounds. The magnetic ordering - type in the function of temperature is discussed. Then the electronic structure of these compounds is presented. The third part concentrates on magnetically hard intermetallics
EN
The compounds of the Rn+1Co3n+5B2n family crystallize in a hexagonal structure having the P6/mmm space group. The ab initio spin-polarized band structure calculations have been performed based on the tight-binding linear muffin-tin orbitals method (TB LMTO) for the following five representatives of the family: RCo5, RCo4B, R3Co11B4, R2Co7B3 and RCo3B2, where R=Gd or Tb. The cobalt atoms occupying distinct sites have different types and numbers of neighbouring atoms and as a consequence the magnetic moments are different. The calculated values are compared with the bulk measurements.
EN
Amorphous hydrogenated germanium oxide films (a-GeXOY:H) fabricated by plasma-assisted chemical vapor deposition (PACVD) from a mixture of oxygen and tetramethylgermane in radio-frequency (13.56 MHz) glow discharge, were investigated. Measurements of electrical conductivity and internal photoemission were carried out. It has been found that the films are amorphous insulators (a-I) with the transport gap of 6.7 eV and the conductivity of the order of 10–14 S/m. To characterize the chemical structure of the films, Raman spectroscopy was used. The main structure of the GeO4 type with low concentration of Ge–Ge and Ge–C bonds has been identified.
20
Content available remote Tomografia pozytonowa w fizyce i medycynie
PL
Badanie kwantów anihilacji pary elektron-pozyton ma zastosowanie zarówno w diagnostyce medycznej, jak i fizyce ciała stałego. Wykorzystanie tego samego zjawiska fizycznego, jak i podobnej aparatury, pozwala badać właściwości obiektu albo w przestrzeni położeń, albo w przestrzeni pędu (odpowiednio, badania medyczne lub fizyczne). W pracy przedstawiono metody matematyczne tomografii komputerowej; zastosowanie emisyjnej tomografii komputerowej w badaniach procesów fizjologicznych oraz diagnozie różnych chorób; pomiar dwuwymiarowych korelacji kątowych promieniowania anihilacyjnego w celu badania struktury elektronowej (w szczególności powierzchni Fermiego) oraz efektów korelacji elektron-pozyton (lub elektron-elektron) w ciałach stałych o charakterze metalicznym.
EN
Studies of electron-positron annihilation rays has been successfully employed both in medicine and solid state physics. The same phenomenon as well as a similar equipment allow us to study either the real or the momentum space (medical or physical investigations, respectively). In the paper the mathematical methods of computed tomography; applications of positron emmision tomography for studying physiological processes and in diagnosis of different illnesses; measurements of two-dimensional angular correlation of annihilation radiation spectra to probe electronic structures (particularly, the Fermi surface) and electron-positron (or electron-electron) correlation effects in metallic solids are presented.
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