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1
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Electronic Structure and Magnetic Properties of the UPdAs_2 Compound

100%
Werwiński M., Szajek A.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1148-1150
EN
The electronic band structure of UPdAs_2 is calculated using full potential linearized augmented plane wave implemented in the WIEN2k code. Calculations were started with the exchange-correlation potential in the form proposed by Perdew, Burke and Ernzerhof (PBE). We additionally studied PBE+U approach with the Coulomb repulsion energies U applied to the uranium 5f orbital and varying from 0 to 4 eV. PBE+OP with orbital polarization term was one more tested approach. To reproduce magnetic sequence ++- a doubled in c axis supercell is built. Initial magnetic moments on inequivalent uranium atoms are assumed to be opposite. The antiferromagnetic ground state is confirmed by comparison of total energies calculated for various magnetic configurations. Results of PBE+U(1.0 eV)+J(0.5 eV) and PBE+OP approaches are in the best agreement with the neutron scattering measurements of magnetic moments. The calculated total magnetic moment on uranium atoms is predicted to be equal to 1.47 μ_{B}.
2
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The Electronic and Magnetic Properties of UGe Compound

100%
Werwiński M., Szajek A.
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issue 5
886-887
EN
The UGe system crystallizes in the orthorhombic ThIn-type structure. The uranium atoms occupy three crystallographic sites with interatomic U-U distances like below and above the Hill limit. The band structure has been calculated by using the density functional theory and generalized gradient approximation. Ab initio calculations were performed based on the full-potential local-orbital minimum-basis code. Calculations showed that all three types of uranium atoms are magnetically ordered with antiparallel alignment of the magnetic moments. For uranium atoms with an interatomic distance below the Hill limit magnetic moments are significantly reduced due to hybridization effects.
3
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Electronic Structure and Magnetic Properties οf the UCoAs_{2} Compound

100%
Werwiński M., Szajek A.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
244-246
EN
The UCoAs_{2} compound crystallizes in the tetragonal HfCuSi_{2} type structure with space group P4/nmm. The compound orders ferromagnetically at 150 K with a spontaneous magnetic moment of about 1.8 μ_B per formula unit. We present results of fully relativistic band structure calculations based on the full-potential local-orbital minimum-basis scheme (FPLO-5.10-20) and compare magnetic moments obtained from calculations without and with orbital polarization corrections. The magnetic behavior of the Co atoms remains unknown.
4
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The Electronic and Magnetic Properties οf UNiAs_2 Antiferromagnet

81%
Werwiński M., Szajek A., Leśniak P., Malinowski W.
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issue 2
413-416
EN
UNiAs_2 band structure has been calculated based on two full-potential methods: full potential linearized augmented plane wave implemented in WIEN2k code and full-potential local-orbital minimum-basis in FPLO code. Starting from the local (spin) density approximation (L(S)DA) we verified either the orbital polarization correction or the LSDA+U approach with the Coulomb repulsion energies U of 0-4 eV for the uranium 5f electrons. Calculated magnetic moments confirm antiferromagnetic ground state and collinear magnetic sequence. The best agreement with experimental results has been achieved by applying orbital polarization corrections, the magnetic moment on uranium amounts to 1.76 μ_{B} per U atom.
5
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Magnetic Properties of the U_5Ge_4 Compound Based on Ab initio Calculations

81%
Szajek A., Werwiński M., Malinowski W., Leśniak P.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
251-253
EN
U_5Ge_4 crystallizes in a hexagonal Ti_5Ga_4 type structure with two inequivalent crystallographic sites occupied by uranium atoms. The band structure calculations were performed by the full-potential local-orbital minimum basis band structure code. The calculations showed that on both types of uranium atoms small magnetic moments are formed and their values are equal to 0.08 and 0.15 μ_{B}/atom, respectively.
6
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Electronic Properties of CeNiAl₄ Based on ab initio Calculations and XPS Measurements

81%
Werwiński M., Chełkowska G., Szajek A., Kowalczyk A.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
517-519
EN
The CeNiAl₄ compound crystallizes in an orthorhombic YNiAl₄-type structure with a Cmcm space group. The earlier susceptibility data and X-ray photoelectron spectroscopy (XPS) suggested a localized character of the 4f states in CeNiAl₄ with a valence state close to a Ce⁺³ ion. In this work we present a combined theoretical and experimental study of the electronic structure for the Kondo dense system CeNiAl₄ based on the XPS data and ab initio calculations. Using the band structure calculations the theoretical XPS valence band spectra are evaluated. Below the Fermi energy the total density of states contains mainly 3d states of Ni hybridized with Ce 4f states.
7
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The Electronic and Magnetic Properties οf Yb_xGd_{1-x}Ni_5 Systems

71%
Szajek A., Werwiński M., Chełkowska G., Bajorek A., Chrobak A.
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issue 5
905-906
EN
The intermetallic compounds Yb_{x}Gd_{1 - x}Ni_5 crystallize in the hexagonal CaCu_5-type structure. Based on wide ranging SQUID-type magnetometer, it was shown that the saturation magnetization decreases with growing concentration of ytterbium. The opposite tendency was observed for the Sommerfeld coefficient obtained in the heat capacity measurements. These results are confirmed using ab initio band structure calculations.
8
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Electronic Structure and Magnetic Properties of Ce_5CuPb_3 Based on Ab Initio Calculations

71%
Werwiński M., Szajek A., Leśniak P., Malinowski W., Stasiak M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1182-1184
EN
Ce_5CuPb_3 band structure has been calculated based on two ab initio methods: full potential-linearized augmented plane wave implemented in WIEN2k code and full-potential local-orbital minimum-basis in FPLO code. The calculations were performed with and without spin polarization. Starting from the generalized gradient approximation we additionally tested either an orbital polarization correction and the GGA+U approach with the Coulomb repulsion energies U varied from 0 to 6.7 eV within the Ce 4f electron shell. The calculations confirmed possible antiparallel alignment of the magnetic moments of the cerium atoms in the low temperature phase.
9
Content available remote

Influence of Valence Band Modifications on Hydrogen Absorption in Zr-Pd Alloy Thin Films

61%
Jabłoński B., Pacanowski S., Werwiński M., Marczyńska A., Dawczak-Dębicki H., Szajek A., Smardz L.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
620-623
EN
We study the valence band modifications of in-situ prepared nano- and polycrystalline Pd-Zr alloy thin films using X-ray photoelectron spectroscopy. Results were compared with valence bands calculated by ab initio methods. Furthermore, hydrogen absorption and desorption kinetics under pressure of about 570 mbar were studied in Pd covered nanocrystalline ZrPd₂ alloy thin film. Results showed that modifications of the valence band of the nanocrystalline alloy thin film could significantly influence on hydrogen absorption and desorption process.
10
Content available remote

XPS and UPS Valence Band Studies of Nanocrystalline Ni-Ti Alloy Thin Films

52%
Pacanowski S., Skoryna J., Szajek A., Marczyńska A., Dawczak-Dębicki H., Werwiński M., Majchrzycki Ł., Smardz L.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
613-616
EN
In this contribution we study valence bands of in-situ prepared nanocrystalline NiTi and Ni₃Ti alloy thin films using X-ray and ultraviolet photoelectron spectroscopy. Additionally, theoretical valence band of NiTi alloy was calculated by ab-initio methods. The structure and morphology of the samples were studied by X-ray diffraction and atomic force microscopy, respectively. Furthermore, hydrogen absorption and desorption kinetics at a pressure of about 1000 mbar were studied in Pd covered nanocrystalline NiTi alloy thin film using four-point resistivity measurements. Results showed that modifications of the valence bands of the Ni-Ti thin films due nanocrystalline structure can influence on the room temperature hydrogen absorption and desorption kinetics.
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