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1
Content available remote

Calculations of Transition Probabilities for Some Excited Levels of Na I

100%
Çelik G., Ateş Ş.
Acta Physica Polonica A
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2008
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vol. 113
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issue 6
1619-1627
EN
Transition probabilities are calculated for individual and multiplet lines between some excited states in neutral sodium by using the weakest bound electron potential model theory. In the determination of parameters required for calculation of transition probabilities, we employed numerical non-relativistic Hartree-Fock wave functions for expectation values of radii in all levels. The necessary energy values were taken from experimental energy data in the literature. The obtained results were compared with accepted values taken from National Institute of Standards and Technology data and multi-configurational Hartree-Fock results given by Fischer. A good agreement was observed in related excited states.
2
Content available remote

Oscillator Strengths of the 1s2s^{1}S^{e} → 1s2p^{1}P^{0} Transition in He

100%
Tiwary S., Kumar P.
|
|
issue 1
23-28
EN
The paper presents configuration interaction (CI) calculations of both the length and velocity forms of the oscillator strengths for 1s2s^{1}S^{e} → 1s2p^{1}P^{0} transition in the He atom. For the first time the agreement between the length and velocity values to within about 0.045% has been achieved.
3
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Rigid and Relaxed Diagonal Orbital Hardnesses of the Valence Shell of Transition Metal Ions from Xα Calculations

100%
Antonova T., Neshev N., Proinov E. I., Nalewajski R. F.
Acta Physica Polonica A
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1991
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vol. 79
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issue 6
805-815
EN
Valence shell diagonal hardnesses (electron repulsion) parameters are reported for the first- and second-row transition metal ions, determined via finite differences from the Xα eigenvalues for alternative configurations and charges. Both rigid (unrelaxed orbitals) and orbitally relaxed hardnesses have been calculated. The relaxed parameters provide a convenient basis for generating a realistic hardness tensor of catalytic systems involving transition metals at the atoms-in-molecules (AIM) oxidation state and configurations, thus facilitating the charge-sensitivity-analysis of chemisorption systems both at the AIM and orbital resolutions. The observed trends in the orbital relaxation effects are briefly discussed.
4
Content available remote

Jahn-Teller Center as Quasiparticle of Fractional Statistics

63%
Sobolewski A. L.
Acta Physica Polonica A
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1995
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vol. 88
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issue 2
305-313
EN
Arguments are presented towards the identification of a molecular center undergoing a linear E⊗e Jahn-Teller effect as a quasiparticle of fractional statistics. The relevance of Jahn-Teller quasiparticles for the description of the type-II superconductivity is briefly discussed.
5
Content available remote

Quantum Mechanical Studies of Bond and Molecular Polarizabilities of Gas-Phase Metal Halides

63%
Pandey A., Bigotto A., Gulati R.
|
|
issue 4
503-520
EN
The bond and molecular polarizabilities are studied for the gas-phase metal halides using delta-function potential model of chemical binding on the basis of quantum mechanical approach. The applicability of the model is demonstrated. The contribution of the polarity corrections for the metal halides is thoroughly investigated and it has been found that it plays a significant role for fluorides. Our polarizability calculations resolve the discrepancy about the conformation of the barium dichloride and mercury dichloride and favour the nonlinear structure. Due to lack of experimental results for most of halides of transition metals, the decision whether to incorporate polarity corrections or not remains uncertain at this stage: we must await measurements of more experimental values before we reach any final conclusion. The ionic bond orders have been used for the first time to investigate polarizabilities of monomers and dimers of alkali halides. The results for dimers reveal that polarity contribution is essential for the lithium halides dimers and not for other dimers. The computed results will be asset for the interpretation of experimental measurements.
6
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Racah Recoupling Matrices for System of Two Free Electrons Confined To Single Star

51%
Lulek T., Kłos J.
Acta Physica Polonica A
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1996
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vol. 90
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issue 3
483-490
EN
Racah-Wigner type of calculus is adapted to the system of two free electrons in a cubic box, confined to a single star p00 of quasimomentum. Various coupling schemes (LS-like, jj-like, and transitive) have been reviewed in analogy to the case of a free atom. Racah recoupling matrices are calculated explicitly, and their quantum-mechanical meaning is exposed in terms of octahedral multipoles.
7
Content available remote

Ground States of Helium Atom and Hydrogen Negative Ion in the Presence of Magnetic Field Using Variational Monte Carlo Technique

51%
Doma S., Shaker M., Farag A., El-Gammal F.
|
EN
Using variational Monte Carlo method, we calculated the 1^1 0^{+} state energies, the derivatives of the total energy and the ionisation energies of the helium atom, and hydrogen negative ion in the presence of magnetic field regime between 0 a.u. and 10 a.u. Our calculations are based on using two types of compact and accurate trial wave functions used before to calculate energies in the absence of magnetic field. Our results are in good agreement with the most recent previous accurate values and also with the exact values.
8
Content available remote

DFT and TD-DFT Calculations of Some Metal Free Phthalonitrile Derivatives for Enhancement of the Dye Sensitized Solar Cells

51%
Anbarasan P., Senthil Kumar P., Vasudevan K., Moorthy Babu S., Aroulmoji V.
Acta Physica Polonica A
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2011
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vol. 119
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issue 3
395-404
EN
The geometries, electronic structures, polarizabilities, and hyperpolarizabilities of organic dye sensitizers 3,4-pyridinedicarbonitrile, 3-aminophthalonitrile, 4-aminophthalonitrile and 4-methylphthalonitrile were studied based on density functional theory using the hybrid functional B3LYP. Ultraviolet-visible spectra were investigated by time dependent density functional theory. The features of electronic absorption spectra in the visible and near-UV regions were assigned based on time dependent density functional theory calculations. The absorption bands are assigned to π → π* transitions. Calculated results suggest that the three lowest energy excited states of 3,4-pyridinedicarbonitrile, 3-aminophthalonitrile, 4-aminophthalonitrile and 4-methylphthalonitrile are due to photoinduced electron transfer processes. The interfacial electron transfer between semiconductor TiO_2 electrode and dye sensitizers 3,4-pyridinedicarbonitrile, 3-aminophthalonitrile, 4-aminophthalonitrile and 4-methylphthalonitrile is due to an electron injection process from excited dyes to the semiconductor's conduction band. The role of amide and methyl groups in phthalonitrile in geometries, electronic structures, and spectral properties were analyzed in a comparative study of 3,4-pyridinedicarbonitrile, 3-aminophthalonitrile, 4-aminophthalonitrile and 4-methylphthalonitrile for the improvement of dye sensitized solar cells.
9
Content available remote

Investigation of Relations between Atomic Number and Composition Weight Ratio in PZT and SMA and Prediction of Mechanical Behavior

51%
Monfared V., Khalili M.
Acta Physica Polonica A
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2011
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vol. 120
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issue 3
424-428
EN
In this paper there is presented the mechanical behavior of the one lead-zirconate-titanate by its atomic number and its certain mechanical behavior is simulated by the mathematical modeling and ABAQUS software for smart materials, as well as prediction of mechanical behaviors. Also in this smart material (Pb-Zr-Ti) the grain size according to molar ratio is studied. This mechanical behavior is modeled by the exponential and polynomial formula from one to ten degree. Next there are defined the new relations for mechanical behavior and composition weight ratio, between composed elements for triplex lead-zirconate-titanate and dual smart materials. Triplex lead-zirconate-titanate has been selected as main and important material for the development of smart structures. In addition, the relation between atomic number and weight ratio in one smart material (Ni-Ti) is investigated briefly. In this work, change of resistance and voltage, pressure, grain size, molar ratio, residual stress, content of zirconate and the other mechanical properties are studied.
10
Content available remote

Problems Associated with Transferring of Engineering to Small Scale - Towards Theoretical Nanotechnology

45%
Kaczmarek J.
Acta Physica Polonica A
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2016
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vol. 130
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issue 6
1295-1323
EN
This paper is seen as a review of attempts carried out by author in order to indicate problems related to transferring of engineering to smaller scales having in mind theoretical aspects. Two main problems are indicated. The first one is associated with question what kind of theory is appropriate for realization of design of devices and processes related to smaller scales including nanoscale. The second problem is related to determination of source of precision which is necessary for realization of the design. Solution of both problems needs elaboration of appropriate theories. One indicates that unified mechanics of materials based on collection of dynamical systems with dimensional reduction is appropriate for future realization of the design process. This is multi-scale description which unifies discrete models related to atomic scale, including molecular dynamics, and more averaged continuum descriptions. In order to determine corresponding source of precision for small scale processes the vacuum medium mechanics is introduced. Within vacuum medium mechanics we are able to determine attractor, expressed on the most fundamental elementary particle level, and responsible for self-organization manifested in molecular processes. Vacuum medium mechanics is considered as fundamental theory. Therefore we should estimate to what degree such a theory is stable with respect to large set of experimental results. In particular one investigates consequences of vacuum medium mechanics for theoretical biology. One accentuates that mechanisms of biological evolution and source of precision for nanotechnology expressed by means of vacuum medium mechanics are interrelated. Theoretical biology and nanotechnology should be described in consistent way in order to cooperate in a future. Both theories: unified mechanics of materials and vacuum medium mechanics are seen as basis for further development of theoretical nanotechnology.
11
Content available remote

Fullerenes as polyradicals

38%
Sheka E.
Open Physics
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2004
|
vol. 2
|
issue 1
160-182
EN
We present the investigation of the electronic structure of X60 molecules (X=C, Si), containing 60 odd electrons with spin-dependent interaction between them. Conditions for the electrons to be excluded from the covalent pairing are discussed. A computational spin-polarized quantum-chemical scheme is suggested to evaluate four parameters-energy of radicalization, exchange integral, atom spin density, and squared spin- to characterize the effect quantitatively. A polyradical character of the species, weak for C60 and strong for Si60, is established.
12
Content available remote

Application of the Electron Theory of Sintering to the Ferrite Systems

38%
Kopayev A., Bushkova V.
Acta Physica Polonica A
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2010
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vol. 117
|
issue 1
30-33
EN
The compositions of magnesium-zinc ferrites (Mg_{0.56}Zn_{0.44})_{1-y}Fe_{2 + 2y/3}O_{4}, where y = -0.05, 0, +0.05 were sintered at temperatures 1230 and 1280°C. The analysis of the kinetics of sintering was carried out by using the Ivensen model. It was shown that at decrease of y the sintering rate increases. The analysis of the electronic configurations of the cations in the ferrite composition showed the possibility of applying the Samsonov electronic theory of sintering powders to them. Magnetic permeability of the studied chemical compositions increases with increase of the density of ferrites as well as with the temperature and the time of isothermal soaking.
13
Content available remote

Towards relativistic ECP / DFT description of chemical bonding in E112 compounds: spin-orbit and correlation effects in E112X versus HgX (X=H, Au)

32%
Zaitsevskii A., Rykova E., Mosyagin N., Titov A.
Open Physics
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2006
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vol. 4
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issue 4
448-460
EN
The relativistic effective core potential (RECP) approach combined with the spin-orbit DFT electron correlation treatment was applied to the study of the bonding of eka-mercury (E112) and mercury with hydrogen and gold atoms. Highly accurate small-core shape-consistent RECPs derived from Hartree-Fock-Dirac-Breit atomic calculations with Fermi nuclear model were employed. The accuracy of the DFT correlation treatment was checked by comparing the results in the scalar-relativistic (spin-orbit-free) limit with those of high level scalar-relativistic correlation calculations within the same RECP model. E112H was predicted to be slightly more stable than its lighter homologue (HgH). The E112-Au bond energy is expected to be ca. 25–30 % weaker than that of Hg-Au. The role of correlations and magnetic (spin-dependent) interactions in E112-X and Hg-X (X=H, Au) bonding is discussed. The present computational procedure can be readily applied to much larger systems and seems to be a promising tool for simulating E112 adsorption on metal surfaces.
14
Content available remote

Multi-mode ground state interaction terms in C60-based electron donor-acceptor complexes

26%
Sheka E.
Open Physics
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2004
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vol. 2
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issue 2
300-328
EN
Quantum-chemical testing of donor-acceptor properties of binary molecular complexes, related to the singlet state, is suggested as QCh calculations of studied systems and their constituents by using both spin-nondependent (RHF) and spindependent (UHF) versions of the exploited computational tool. The avoided crossing of intermolecular interaction terms of neutral moleculesE int(A 0 B 0) and molecular ionsE int(A + B −) causes a multi-mode character of the ground state term. The dependence of D-A complex properties on the type of the term, space positions of the term minimum, and the interrelation of the corresponding energies are discussed. The suggested approach has been applied to binary complexes C60+X (X=TAE, TDAE, DMMA, COANP, 2Li, Mg).
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