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    Wyświetlanie 1-10 z 10
    Tytuł:
    Crystal structures and conformers of CyMe4-BTBP
    Autorzy:
    Lyczko, K.
    Ostrowski, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/147806.pdf
    Data publikacji:
    2015
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    conformers
    crystal structure
    CyMe4-BTBP
    DFT calculations
    Opis:
    The crystal structure of new conformation of the CyMe4-BTBP ligand (ttc) has been presented. The ttt conformer of this compound in a form of THF solvate has been also crystallized. The geometries of six possible conformations (ttt, ttc, tct, tcc, ctc and ccc) of the CyMe4-BTBP ligand have been modeled in the gas phase and in solutions (MeOH and H2O) by DFT calculations using B3LYP/6-31G(d,p) method. According to the calculations, in the three different media the conformers with trans orientation of the N atoms in the bipyridyl moiety are the most stable.
    Źródło:
    Nukleonika; 2015, 60, No. 4, part 2; 853-857
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Bonding xenon and krypton on the surface of uranium dioxide single crystal
    Autorzy:
    Dąbrowski, L.
    Szuta, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/147310.pdf
    Data publikacji:
    2014
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    noble gases
    uranium dioxide
    chemical bond
    DFT
    GGA
    Opis:
    We present density functional theory (DFT) calculation results of krypton and xenon atoms interaction on the surface of uranium dioxide single crystal. A pseudo-potential approach in the generalised gradient approximation (GGA) was applied using the ABINIT program package. To compute the unit cell parameters, the 25 atom super-cell was chosen. It has been revealed that close to the surface of a potential well is formed for xenon and krypton atom due to its interaction with the atoms of oxygen and uranium. Depth and shape of the well is the subject of ab initio calculations in adiabatic approximation. The calculations were performed both for the case of oxygenic and metallic surfaces. It has been shown that the potential well for the oxygenic surface is deeper than for the metallic surface. The thermal stability of immobilising the atoms of krypton and xenon in the potential wells were evaluated. The results are shown in graphs.
    Źródło:
    Nukleonika; 2014, 59, 3; 83-89
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Spin trapping studies of essential oils in lipid systems
    Autorzy:
    Makarova, K.
    Drązikowska, K.
    Suska, B.
    Zawada, K.
    Wawer, I.
    Powiązania:
    https://bibliotekanauki.pl/articles/147786.pdf
    Data publikacji:
    2015
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    spin trapping ESR
    essential oils
    DFT calculations
    lipids
    Opis:
    In the present work, we report the results of a spin trapping ESR study of four essential oils widely used for skin care products such as creams and bath salts. The studied essential oils are Rosmarini aetheroleum (rosemary), Menthae piperitae aetheroleum (mint), Lavandulae aetheroleum (lavender), and Thymi aetheroleum (thyme). Fenton reaction in the presence of ethanol was used to generate free radicals. The N-tert- -butyl-α-phenylnitrone (PBN) was used as a spin trap. In the Fenton reaction, the rosemary oil had the lowest effect on radical adduct formation as compared to the reference Fenton system. Since essential oils are known to be lipid soluble, we also conducted studies of essential oils in Fenton reaction in the presence of lipids. Two model lipids were used, namely 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dipalmitoyl-sn- -glycero-3-phosphocholine (DPPC). The obtained results suggested that in the presence of DOPC lipids, the •OH and PBN/•CHCH3(OH) radicals are formed in both phases, that is, water and lipids, and all the studied essential oils affected the Fenton reaction in a similar way. Whereas, in the DPPC system, the additional type of PBN/X (aN = 16.1 G, aH = 2.9 G) radical adduct was generated. DFT calculations of hyperfi ne splittings were performed at B3LYP/6-311+G(d,p)/EPR-II level of theory for the set of c-centered PBN adducts in order to identify PBN/X radical.
    Źródło:
    Nukleonika; 2015, 60, No. 3, part 1; 461-468
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Mössbauer spectroscopy of reduced forms of a Fe-tetraphenylporphyrine complex
    Autorzy:
    Kaczmarzyk, T.
    Rutkowska, I.
    Dziliński, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/148211.pdf
    Data publikacji:
    2015
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    DFT calculations
    electronic structure
    iron-(tetraphenyl)porphyrin
    Mössbauer spectroscopy
    reduction process
    Opis:
    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.
    Źródło:
    Nukleonika; 2015, 60, 1; 51-55
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    EPR study on sugar radicals utilized for detection of radiation treatment of food
    Autorzy:
    Guzik, G. P.
    Stachowicz, W.
    Michalik, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/146706.pdf
    Data publikacji:
    2012
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    density functional theory (DFT)
    dried fruits
    electron paramagnetic resonance (EPR)
    irradiation
    mannose
    sorbose
    Opis:
    Radicals produced by ionizing radiation in sugars, the components of dried and raw fruits give rise to stable multicomponent electron paramagnetic resonance (EPR) signals unidentified so far. The subject of the present EPR study is to identify the radicals stabilized in gamma-irradiated crystalline sugars, D(+)mannose and L(-)sorbose extracted from cranberries (Vaccininum oxycoccos) and rowan berries (Sorbus aucuparia), respectively. EPR measurements and density functional theory (DFT) simulations were employed for that purpose.
    Źródło:
    Nukleonika; 2012, 57, 4; 545-549
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Local structure and cohesive properties of mixed thorium and uranium dioxides calculated by "ab initio" method
    Autorzy:
    Dąbrowski, L.
    Szuta, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/147874.pdf
    Data publikacji:
    2012
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    uranium
    thorium dioxide
    DFT+U
    LDA
    GGA
    local structure
    cohesive properties
    bulk modulus
    Opis:
    Density functional theory (DFT) results of calculations of the mixed thorium and uranium dioxide Th1-xUxO2 for the following mole ratio x = 0, 0.25, 0.75 and 1 are presented and discussed. "Ab initio" calculations were performed using the Wien2k program package. To compute the unit cell parameters the 12 atom super-cell were chosen. The lattice parameters were calculated through minimization of the total energy by the change of lattice parameters and atom displacement within the unit cell. Calculations were performed for five different exchange energy approximations EXC with and without corrective orbital potential U, and obtained lattice constants are presented graphically and compared with experimental data. It is established that the initially assumed oxygen location within the unit cell plus or minus 0.25 of the mixed compounds are not their equilibrium positions. The oxygen atoms within the unit cell undergo dislocation in the (111) direction. So, the distances oxygen-uranium are smaller than the distances oxygen-thorium. The change of local structure is presented graphically and appropriate parameters values are given in Table. The bulk modulus and the cohesive properties are also counted and shown graphically.
    Źródło:
    Nukleonika; 2012, 57, 1; 101-107
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    „Ab initio” study of helium atoms immobilization in UO2 crystals
    Autorzy:
    Dąbrowski, L.
    Szuta, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/146654.pdf
    Data publikacji:
    2012
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    uranium
    dioxide
    DFT+U
    LDA
    GGA
    ABINIT
    over-barrier jumps
    incorporated helium
    harmonic oscillator
    Opis:
    We present density functional theory (DFT) calculation results concerning the uranium dioxide crystals with a helium atom incorporated in the octahedral interstitial position. "Ab initio" calculations were performed using the Wien2k program package. For comparison, a pseudo-potential approach in the generalized gradient approximation was applied using the ABINIT program package. To compute the unit cell parameters 13 atom super-cell was chosen. Parameters of the potential barrier, which the helium atom has to overcome while jumping to the next octahedral interstitial position, were calculated by the help of both the program packages. The results, obtained using two different program packages, are shown in the table and presented graphically. For the so described parameters, the quantum mechanical movement of the helium atom around the equilibrium position is considered. The parameters of Schrödinger's equation are collected in Table 2, while the results of mean square deviation and thermal occupation of energetic levels are presented in a graph. It is established that the helium atoms are located (with an accuracy of several percent of lattice constant) nearby the equilibrium position and form a local bound state. Applying a two site-model, we evaluated the time for an over-barrier jump. Graphically presented results show that the helium atom over-barrier jump is not possible even for temperatures as high as 1200 K. Influence of potential barrier height on the jump time was also considered.
    Źródło:
    Nukleonika; 2012, 57, 3; 337-343
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Bonding xenon on the surface of uranium dioxide single crystal
    Autorzy:
    Dąbrowski, L.
    Szuta, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/147186.pdf
    Data publikacji:
    2013
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    noble gases
    uranium dioxide
    chemical bond
    density functional theory (DFT)
    generalized gradient approximation (GGA)
    Opis:
    We present density functional theory (DFT) calculation results of xenon atom interaction with the surface of uranium dioxide single crystal. A pseudo-potential approach in the generalized gradient approximation (GGA) was applied using the ABINIT program package. It has been revealed that close to the surface a potential well is formed for xenon atom due to its interaction with the atoms of oxygen and uranium. Depth and shape of the well is the subject of “ab initio” calculations. The calculations were performed both for the case of oxygenic and metallic surfaces. It has been shown, that the potential well for the oxygenic surface is deeper than for the metallic surface.
    Źródło:
    Nukleonika; 2013, 58, 4; 453-458
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Diffusion of helium in the perfect uranium and thorium dioxide single crystals
    Autorzy:
    Dąbrowski, L.
    Szuta, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/147700.pdf
    Data publikacji:
    2013
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    uranium
    thorium dioxide
    diffusion
    tunneling
    DFT+U
    generalized gradient approximation (GGA)
    potential barrier
    incorporated helium
    Opis:
    We present quantum-mechanical evaluation of helium diffusion coefficient in the crystalline UO2 and ThO2. Parameters assignment of Schrödinger’s equation were done using the crystal field potentials which were obtained applying the density functional theory (DFT). “Ab initio” calculations were performed using the Wien2k program package. To compute the unit cell parameters the 13 atom super-cell was chosen. Applying two-site model we evaluated the time for an over-barrier jump and diffusion of interstitial He. The obtained values for diffusion coefficient are compared with the experimentally obtained values and with the theoretical values of other authors. In addition, it is simultaneously shown that helium diffusion in these materials is a quantum diffusion.
    Źródło:
    Nukleonika; 2013, 58, 2; 295-300
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Mössbauer study of a tetrakis (pentafl uorophenyl) porphyrin iron (III) chloride in comparison with the fluorine unsubstituted analogue
    Autorzy:
    Kaczmarzyk, T.
    Dziedzic-Kocurek, K.
    Rutkowska, I.
    Dziliński, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/146091.pdf
    Data publikacji:
    2015
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    catalytic activity
    DFT calculations
    electronic structure
    iron(III)-[tetrakis (pentafl uorophenyl)]
    Mössbauer spectroscopy
    porphyrin chloride
    Opis:
    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.
    Źródło:
    Nukleonika; 2015, 60, 1; 57-61
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-10 z 10

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