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1
Content available remote

Elastic Properties, Mechanical Stability, and State Densities of Aluminnides

100%
Zhang B., Jia Z., Duan X., Jia Z.
Acta Physica Polonica A
|
2013
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vol. 123
|
issue 4
668-672
EN
First-principles calculations were performed to study on alloying stability, electronic structure, and mechanical properties of Al-based intermetallic compounds. The results show that the lattice parameters obtained after full relaxation of crystalline cells are consistent with experimental data. The calculation of cohesive energies indicated that the structure stability of these Al-based intermetallics will become higher with increasing Zr element in crystal. The calculations of formation energies showed that AlCu_2Zr has the strongest alloying ability, followed by AlZr_3 and finally the AlCu_3. Further analysis finds out that single-crystal elastic constants at zero-pressure satisfy the requirement of mechanical stability for cubic crystals. The calculations on the ratio of bulk modulus to shear modulus reveal that AlCu_2Zr can exhibit a good ductility, followed by AlCu_3, whereas AlZr_3 can have a poor ductility; however, for stiffness, these intermetallics show a converse order. The calculations on Poisson's ratio show that AlCu_3 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 AlCu_3, Cu 3d and Zr 4d states for AlCu_2Zr, and Al 3s, Zr 5s and 4d states for AlZr_3, respectively; in particular, the electronic structure of the AlZr_3 shows the strongest hybridization, leading to the worst ductility.
2
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Autoionization Rates for Sodium- and Magnesium-Like Tungsten and Gold

63%
Günday Konan G., Özdemir L.
Acta Physica Polonica A
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2017
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vol. 132
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issue 4
1290-1293
EN
The autoionization process has an important role in many areas such as satellite line formation, inner-shell ionization, and diagnostics of astrophysical and fusion plasmas. We have here reported autoionization rates for some levels of Na-like tungsten (W⁶³⁺) and gold (Au⁶⁸⁺), and Mg-like tungsten (W⁶²⁺) and gold (Au⁶⁷⁺) using AUTOSTRUCTURE atomic code. In calculations, the Breit interactions, quantum electrodynamics and configuration interaction effects have been considered. The results obtained for tungsten ions have been compared with other available results. Also new results for gold ions have been presented.
3
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Theoretical Investigation of Electronic Structure and Vibrational Spectra of Conformers of Trinitrotoluene and Trinitrophenol

63%
Kleiza V., Bekešienė S.
Acta Physica Polonica A
|
2011
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vol. 119
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issue 2
189-192
EN
The precise knowledge of vibrational spectra would allow detecting small amounts of these materials by means of spectroscopic methods. The results of the investigation of the vibrational spectra of trinitrotoluene and 2,4,6-trinitrophenol molecules were published in our previous paper, where we investigated the normal state of the molecules. In this paper we present the investigation results of the trinitrotoluene and trinitrophenol molecules conformer's with C_1 and Cs symmetry. We analyzed the potential surfaces and vibration spectra by means of ab initio quantum chemical calculations using basis of Gaussian functions and GAMESS package. Calculations were performed at the Hartree-Fock level and with account of the electron correlation. Personal computers clusters necessary for such investigations were made and SCore parallel environment was used.
4
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Density Functional Study of Bulk and Surface Properties of Rhodium Hydride

51%
Sudhapriyanga G., Asvinimeenaatci A., Rajeswarapalanichamy R., Iyakutti K.
|
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vol. 125
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issue 1
29-35
EN
The electronic properties and structural phase transition of bulk rhodium hydride are analyzed using density functional theory calculations with the generalized gradient approximations. The sequent phase transition is observed in bulk rhodium hydride. The predicted new high pressure phase of rhodium hydride is hexagonal NiAs type. The atomic geometry, adsorption energy, and binding energy of the Rh (111) surface are computed. The calculated surface energy for Rh (111) surface is 1.06349 eV and the maximum adsorption energy is obtained in 6×1 phase as 2.8617 eV. The relaxed geometries show that hydrogen has a strong influence on the interlayer distance.
5
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Structure and Vibrational Studies of ±1-(1H-Benzoimidazol-2-YL) Ethanol, Using DFT Method

51%
Oturak H., Kaya Kinaytürk N., Şahın G.
Acta Physica Polonica A
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2015
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vol. 128
|
issue 2B
B-417-B-421
EN
In this study, conformational analysis and quantum chemical calculations of ±1-(1H-Benzoimidazol-2-YL) Ethanol were carried out. The geometric structure, infrared intensities, UV-VIS spectrum, HOMO-LUMO energies, ^1H and ^{13}C nuclear magnetic resonance (NMR) chemical shifts were calculated by using the density functional method (DFT/B3LYP) with 6-311++G(d,p) basis set. The vibrational studies were interpreted in terms of potential energy distribution (PED). Finally, calculated values were compared with the experimental ones.
6
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Structural Parameters and Electronic Structure of Monolayers of Transition Metal Dichalcogenides from Ab Initio Calculations

51%
Woźniak T., Scharoch P., Winiarski M.
Acta Physica Polonica A
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2016
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vol. 129
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issue 1a
A-56-A-58
EN
Structural and electronic properties of the 2H-MX₂ (M = Mo, W; X = S, Se, Te) monolayers are investigated in terms of density functional theory methods. A comparison of structural parameters, energy gaps and spin-orbit coupling driven splittings obtained with different pseudopotential methods and various parametrization of exchange-correlation functional is presented.
7
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H₂ Interaction with rm C₂H₂TM (TM = Sc, Ti, V) Complex Using Quantum Chemical Methods

51%
Tavhare P., Wadnerkar N., Kalamse V., Chaudhari A.
Acta Physica Polonica A
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2016
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vol. 129
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issue 6
1257-1262
EN
This work reports a comparative study of hydrogen uptake capacity of early transition metal atom (Sc, Ti and V) attached to light acetylene (C₂H₂) substrate. Using density functional theory and second order Møller-Plesset method, we predict that maximum of five, five and four hydrogen molecules will be adsorbed on C₂H₂Sc, C₂H₂Ti and C₂H₂V complex, respectively, with respective gravimetric hydrogen uptake capacity of 12.43, 12, and 9.48 wt%. All the interactions between hydrogen molecules and organometallic complex are found to be attractive. The highest occupied molecular orbital-lowest unoccupied molecular orbital gap shows that the maximum H₂ adsorbed complexes are kinetically stable. The average binding energies per H₂ molecule for these complexes are within the ideal range for hydrogen storage at ambient conditions. Even after maximum hydrogen molecules adsorption on C₂H₂TM complexes, transition metal atoms remain strongly bound to the C₂H₂ substrate. We have obtained temperature and pressure range over which H₂ adsorption on these three complexes is energetically favorable using the Gibbs free energy corrected H₂ adsorption energy.
8
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Adsorption of Benzene on 4H-SiC (0001) Surface: First Principles Calculations

51%
Tokár K., Majewski J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1049-1051
EN
We study adsorption of the benzene molecule on the Si terminated (0001) surface of 4H-SiC by performing first principles calculations in the framework of density functional theory. We find out that chemical reaction leading to the chemisorption of benzene on the surface has endothermic character. The adsorbed benzene molecule is bounded to two surface Si atoms and it does not lose its integrity, however, it undergoes strong deformations and causes distortion of the substrate. We analyze also changes in the electronic structure caused by benzene adsorption.
9
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Linear and Hyperpolarizabilities of Spiropyran and Derivatives

51%
Sabra M.
Acta Physica Polonica A
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2009
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vol. 115
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issue 3
647-652
EN
The geometry of spiropyran molecule and its derivatives was found using quasi-Newton methods, Broyden-Fletcher-Goldfarb-Shanno technique. Then ab initio quantum chemical methods were applied to calculate the ground state energies of the closed and open forms of spiropyran for different basis sets. The frequency dependent linear polarizability of spiropyran and derivatives were obtained and plotted. The found absorption peaks are different for the closed and the open structures of the spiropyran molecule.
10
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Influence of Spin-Orbit Interaction on Band Structure and Elastic Properties of PbTe

51%
Radzyński T., Łusakowski A.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
954-955
EN
Inclusion of spin-orbit interaction in density functional theory calculations of PbTe band structure leads to wrong results concerning the symmetry of valence and conduction band wave functions. Using two ab initio codes: OpenMX and Quantum Espresso we show that changing the spin-orbit coupling strength in pseudopotentials for Pb it is possible to obtain proper energy gap and wave functions of proper symmetries.
11
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The Influence of Boron Doping Concentration on MgH_{2} Electronic Structure

51%
Kurko S., Paskaš-Mamula B., Matović L., Grbović Novaković J., Novaković N.
Acta Physica Polonica A
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2011
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vol. 120
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issue 2
238-241
EN
We have performed ab initio electronic structure calculations of Mg_{1-x}B_{x}H_{2} compounds with different boron concentrations, ranging from x =0.0625 to 0.5. Full structural relaxation was performed in order to properly describe influence of dopant on host matrix. Results showed that there is a strong influence of boron concentration on structural and thermodynamic stability of compound. B-H bond length is substantially shorter then in Mg-H coordination polyhedron. Boron significantly contributes to density of states at Fermi level within energy gap. The width of boron electronic states heavily depends on boron concentration, causing reduction of energy gap of host MgH_{2}, and leading to metallic nature of compound with highest boron concentration. The predicted thermodynamic instability of compounds with higher boron concentration is in agreement with experimental findings that under similar stoichiometry, boron with magnesium forms only complex hydride, Mg(BH_{4})_{2}. It is also shown that existence of stable hydrides with MgH_{2} rutile structure and small concentration of boron is possible in principle and that boron can be used to further destabilize MgH_{2} in order to enhance its hydrogen sorption-desorption kinetics.
12
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A DFT Study on (001) Thin Slabs of SrTiO_3 and BaTiO_3

51%
Mahmoodi T.
Acta Physica Polonica A
|
2015
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vol. 127
|
issue 6
1616-1620
EN
In this paper, we studied the relaxation of (001) surface of BaTiO_3 and SrTiO_3 slabs with two termination surfaces and with 3, 5, and 7 layers thickness for each cases, using density functional theory and generalized gradient approximation for exchange-correlation functional and pseudo potential method. We calculated the slab energy and the rate of expansion and contraction of the layers and compare them for different thicknesses. Band structure and density of states for these slabs and for BaTiO_3 and SrTiO_3 bulk were computed to find out the variation of band gap with respect to slab thickness. It is found that in comparison with bulk, in TiO_2 slabs of both materials gap size decreases while in SrO and BaO slabs it increases.
13
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Investigation on Mechanical Properties of Mn₃Sb Intermetallic Compound

51%
Boubaker O., Said B.
Acta Physica Polonica A
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2016
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vol. 130
|
issue 1
33-35
EN
In this work, ab initio calculation has been performed to investigate the structural, elastic and mechanical properties of Mn₃Sb intermetallic compound, based on density functional theory plane-wave pseudo potential method within local density approximation and generalized gradient approximation. The calculated structural parameter in both approximations of Mn₃Sb compound is consistent with the experimental data. The elastic constants were determined from a linear fit of the calculated stress-strain function according to the Hooke law. From the elastic constants, the bulk modulus B, shear modulus G, the Young modulus E, the Poisson ratio σ , anisotropy factor A and the ratio B/G for Mn₃Sb compound are obtained. This is the first quantitative theoretical prediction of these properties.
14
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Electronic Band Structure of Ru₃Sn₇

51%
Sahakyan M., Tran V.
Acta Physica Polonica A
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2015
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vol. 127
|
issue 2
303-305
EN
The first-principle band structure calculations for Ru₃Sn₇ and Mo₃Sb₇ were carried out using the full-potential linearized muffin tin orbital method. It was shown that the valence band contribution is mainly due to the 4d electrons of Ru(Mo), while the contribution from the 5p-Sn(Sb) orbitals is relatively small. Furthermore, the 4d and 5p orbitals located near the Fermi level have the non-hybridized characters, thus presumably contributing independently to the total density of states. A comparison of the density of states of two compounds reveals an essential difference in the structures and magnitudes. We estimated the mass enhancement factor and Stoner product and discussed these differences regarding to electronic and magnetic behaviour of these compounds.
15
Content available remote

Formation of Hydrogen Bonds; Hydroxyl and Methyl Groups Dynamics in 2,2-dimethylbutan-1-ol and 2,3-dimethylbutan-2-ol: DFT, IINS and IR Investigations

51%
Juszyńska E., Hołderna-Natkaniec K., Massalska-Arodź M., Natkaniec I., Ściesińska E., Ściesiński J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 4
765-775
EN
Dynamics of 2,2-dimethylbutan-1-ol and 2,3-dimethylbutan-2-ol have been studied by experimental spectroscopy methods, i.e., inelastic incoherent neutron scattering and infrared absorption. Experimental results were discussed and compared with the results of the quantum chemical calculations performed by semi-empirical PM3 and the density functional theory methods assuming the isolated molecule and dimer, trimer and tetramer clusters. The density functional theory modelling of vibrational spectra of monomers and OH bonded molecular clusters allows to assign the inter- and intermolecular vibrational modes observed in density of states and absorption spectra.
16
Content available remote

Impurity Effect on Charge and Spin Density in α-Fe - Comparison between Cellular Model, Ab Initio Calculations and Experiment

51%
Błachowski A., Wdowik U.
Acta Physica Polonica A
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2011
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vol. 119
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issue 1
24-27
EN
The influence of the impurity substituted on the regular site in the BCC α-Fe on charge and spin density on the adjacent iron nuclei has been studied by the ab initio method within framework of the full-potential linearized augmented plane-wave formalism applying density functional theorem. Results were correlated with the phenomenological cellular atomic model of Miedema and van der Woude and with the Mössbauer spectroscopy experimental data.
17
Content available remote

Analysis of Chemical Disorder in Pb_{1-x}Ge_{x}Te

51%
Radzyński T., Łusakowski A.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1317-1322
EN
The PbGeTe crystal lattice is locally deformed due to different ionic radii of cations and their random placement in the lattice. It is important to quantitatively characterize such microscopic disorder because local deformations have significant influence on the properties of magnetic ions introduced to such crystal. The simples method to study microscopic disorder is to consider purely classical model of the lattice in which neighboring atoms are connected by springs with properly chosen spring constant and equilibrium lengths. In the present work, using ab initio methods we discuss applicability of the springs-atoms model to the real crystal. We also explain results of extended X-ray absorption fine structure experiments performed on PbGeTe mixed crystals.
18
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Ab Initio Investigation on the Effect of Transition Metals Doping and Vacancies in WO₃

51%
Mansouri M., Mahmoodi T.
Acta Physica Polonica A
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2016
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vol. 129
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issue 1
8-14
EN
We did a density functional theory spin-polarized calculation based on pseudopotential method on the effect of both vacancy and substitutional impurity in the tungsten tri-oxide lattice. We investigated oxygen and tungsten vacancies and for substitutional dopants we used palladium (Pd), platinum (Pt) and gold (Au) atoms with the formula A_xW_{1-x}O₃ and x=0.125, 0.25, 0.375, 0.5. We obtained electronic band structure, density of states and magnetization of defected and doped WO₃. The results show that in the presence of tungsten vacancy, WO₃ acts as a semiconductor with an indirect band gap while oxygen vacancy induces a metallic behavior for WO₃. Besides, for Pt and Pd the location of trap states lead to photoexcited hole capturing, which can improve photocurrent but for Au dopant, the trap states occur in the middle of the band gap as active recombination centers. Furthermore, both kind of vacancies and Pt dopant can induce magnetization in all values of x, while Pd and Au are less efficient in inducing magnetization.
19
Content available remote

Theoretical Investigation of N-Methyl-N'-(4-nitrobenzylidene) pyrazine-2-carbohydrazide: Conformational Study, NBO Analysis, Molecular Structure and NMR Spectra

45%
Günay N., Tamer Ö., Kuzalic D., Avcı D., Atalay Y.
Acta Physica Polonica A
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2015
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vol. 127
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issue 3
701-710
EN
The crystal structure determination of the methylated pyrazine-2-carbohydrazide derivative, namely N-methyl-N'-(4-nitrobenzylidene)pyrazine-2-carbohydrazide were optimized to obtain its molecular geometric structure and electronic structures at the Hartree-Fock and density functional theory levels (B3LYP) with 6-311G(d,p) and 6-311++G(d,p) basis sets, using Gaussian 09W programme. The ^{1}H and ^{13}C nuclear magnetic resonance chemical shifts of the title molecule were calculated by using the gauge independent atomic orbital, continuous set of gauge transformations and individual gauges for atoms in molecules methods and were also compared with experimental values. The electronic properties high occupied and low unoccupied molecular orbitals energies were calculated and analyzed. Potential energy surface scan, natural population analysis and Mulliken atomic charges were investigated using theoretical calculations. A detailed molecular picture and intermolecular interactions arising from hyperconjugative interactions and charge delocalization of the molecule were analyzed using natural bond orbital analysis.
20
Content available remote

Electronic and Optical Properties of Heterostructures based on Indium Chalcogenides

38%
Kharkhalis L., Glukhov K., Babuka T.
Acta Physica Polonica A
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2017
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vol. 132
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issue 2
319-321
EN
The models of the heterostructures based on the β-InSe, In₄Se₃ and In₄Te₃ crystals were proposed and the first-principles study of their electronic and optical properties were presented. The band spectra, the spatial distributions of the electron density and the absorption coefficients for different polarizations along crystal axes for the heterostructures of the (In₄Se₃)_m/(In₄Te₃)_m and β-InSe/In₄Se₃ type were calculated. The evolution of the changes in both energy spectrum and optical functions of the heterostructures in comparison with the bulk crystals has been analyzed. Our calculations point out the heterostructures stability and good agreement with the experimental investigations of the photosensitivity in the near and middle infrared region.
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