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    Wyświetlanie 1-5 z 5
    Tytuł:
    Band electronic structure and dielectric functions of (C3N2H5)2SbF5 crystals
    Autorzy:
    Andriyevsky, B.
    Czapla, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/118472.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Koszalińska. Wydawnictwo Uczelniane
    Tematy:
    crystals
    first principles calculations
    electronic structure
    optical properties
    kryształy
    obliczenia z pierwszych zasad
    struktura elektronowa
    właściwości optyczne
    Opis:
    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.
    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.
    Źródło:
    Zeszyty Naukowe Wydziału Elektroniki i Informatyki Politechniki Koszalińskiej; 2016, 10; 51-60
    1897-7421
    Pojawia się w:
    Zeszyty Naukowe Wydziału Elektroniki i Informatyki Politechniki Koszalińskiej
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A Comparative Study of the Effect of Strain on the Electronic and Optical Properties of Filled and Unfilled Ba₈Si₄₆ Type I-clathrate
    Autorzy:
    Mahammedi, N.
    Belkada, R.
    Ferhat, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1031674.pdf
    Data publikacji:
    2017-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    First-principles calculations
    Ba₈Si₄₆
    cage structure mechanical properties
    electronic structure properties
    Opis:
    A first principles calculations study is carried out to theoretically investigate the effect of compressive and tensile strains on the structural, electronic and optical properties of type-I guest-free Si₄₆ and barium-filled Ba₈Si₄₆ clathrates. The electronic band structure of the unfilled Si₄₆ clathrate revealed a semiconducting behaviour with a quasi-direct band gap of 1.36 eV. Under hydrostatic pressure, the bandgap magnitude of the guest-free Si₄₆ behaves monotonously. For the Ba doped Si₄₆ clathrate (Ba₈Si₄₆) structure, the strain has no significant effect on the electronic band structure, while its impact on the optical properties is appreciable. The optical properties, such as the dielectric function and the absorption were computed for different strain variations, which are clearly enhanced for both the unfilled Si₄₆ and Ba-filled Ba₈Si₄₆ clathrates when the pressure is 1 GPa in the direction of a compressive state.
    Źródło:
    Acta Physica Polonica A; 2017, 132, 3; 836-838
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    First-Principles Study of the Structural, Electronic, Magnetic and Thermal Properties of the Cr Doped Ge₆Mn₂Te₈ and Ge₆Fe₂Te₈ Systems
    Autorzy:
    Semari, F.
    Baki, N.
    Khachai, H.
    Yakoubi, A.
    Méçabih, S.
    Khenata, R.
    Shankar, A.
    Rai, D.
    Bouhemadou, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1030079.pdf
    Data publikacji:
    2017-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    first-principles calculations
    half-metallic ferromagnetism
    electronic properties
    magnetic moment
    spin-exchange splitting
    thermodynamic properties
    Opis:
    First-principles calculations have been used to study the structural, electronic, magnetic, and thermal properties of the Cr doped Ge₆Mn₂Te₈ and Ge₆Fe₂Te₈ systems. The calculations were performed using the full-potential linearized augmented plane wave plus local orbitals (FP-LAPW + LO) method based on the spin-polarized density functional theory. Additionally, the electronic exchange-correlation potential is approximated using the spin generalized gradient approximation. The structural properties of the Ge₅Mn₂CrTe₈ and Ge₅Fe₂CrTe₈ alloys are indicated by their corresponding lattice constants, values of the bulk moduli and their pressure derivatives. An analysis of the band structures and the densities of states indicate that for both alloys, they present nearly half-metallic ferromagnetism character. The band structure calculations are used to estimate the spin-polarized splitting energies, Δp_{x}(d) and Δp_{x}(pd) produced by the 3d Mn, 3d Fe and 3d Cr doped states as well as the s(p)-d exchange constants, N₀α (conduction band) and N₀β (valence band). It is observed that the p-d hybridization reduces the magnetic moment of the Mn and Fe atoms from their atomic charge values and create small local magnetic moments on the nonmagnetic Ge and Te sites. Furthermore, the calculations of the charge density indicate that both compounds have ionic bonding character. Through the quasi-harmonic Debye model, the effects of pressure P and temperature T on the bulk modulus B, the primitive cell volume V/V₀, the Debye temperature θ_{D}, the Grüneisen parameter γ, the heat capacity C_{V}, the entropy S, as well as the thermal expansion coefficient, α of the Ge₆Mn₂Te₈, Ge₅Mn₂CrTe₈, Ge₆Fe₂Te₈ and Ge₅Fe₂CrTe₈ alloys are predicted.
    Źródło:
    Acta Physica Polonica A; 2017, 132, 4; 1242-1250
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The ground state structures and magnetic properties of ZrₙNi (n=1-9) clusters from first principles calculation
    Autorzy:
    Zhang, Y.
    Zhu, Z.
    Zhou, X.
    Yang, J.
    Zhu, Y.
    Powiązania:
    https://bibliotekanauki.pl/articles/1054889.pdf
    Data publikacji:
    2017-06
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    first-principles calculations
    ZrₙNi clusters
    the geometric structure of balance
    stability and magnetic properties
    Opis:
    The ground state structures and magnetic properties of ZrₙNi (n = 1-9) clusters are studied by using first principles calculation. Firstly, we find the ground state configurations of ZrₙNi (n = 1-9) clusters. Secondly, the magic clusters (Zr₂Ni and Zr₇Ni) of ZrₙNi clusters are found by the comparisons of average binding energies, the second-order energy difference and energy gaps between the highest occupied orbital and the lowest unoccupied orbital of the ground state of ZrₙNi clusters. Thirdly, the calculated results show that magnetic moment of ZrₙNi (n = 1-2) clusters is 4 μ_{B}; however, the magnetic moment of ZrₙNi clusters is about 2 μ_{B} for n = 3-9 (exception for n = 7). Finally, it is found that the magnetic moment of ZrₙNi cluster mainly comes from Zr atom and Ni atom is the electron acceptor from the Mulliken population analysis.
    Źródło:
    Acta Physica Polonica A; 2017, 131, 6; 1507-1511
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    First-principles calculations of electronic structure of rhodochrosite with impurity
    Autorzy:
    He, Guichun
    Li, Kun
    Guo, Tengbo
    Li, Shaoping
    Huang, Chaojun
    Zeng, Qinghua
    Powiązania:
    https://bibliotekanauki.pl/articles/1449610.pdf
    Data publikacji:
    2020
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    rhodochrosite
    first principles calculations
    electronic structure
    density of states
    Opis:
    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.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2020, 56, 1; 195-203
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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