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Wyświetlanie 1-15 z 35
Tytuł:
A DFT Study on (001) Thin Slabs of $SrTiO_3$ and $BaTiO_3$
Autorzy:
Mahmoodi, T.
Powiązania:
https://bibliotekanauki.pl/articles/1400503.pdf
Data publikacji:
2015-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.15.A-
31.15.E-
82.45.Mp
Opis:
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.
Źródło:
Acta Physica Polonica A; 2015, 127, 6; 1616-1620
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ab Initio Study of Functionalized Carbon Nanotubes
Autorzy:
Milowska, K.
Birowska, M.
Majewski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1791295.pdf
Data publikacji:
2009-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.15.ae
31.15.E-
61.46.Fg
61.48.De
73.22.-f
81.07.De
Opis:
In the present paper, we study the stability of (9, 0), (10, 0), (11, 0) carbon nanotubes functionalized with simple organic molecules $-CH_{n}$ (for n = 2, 3, 4). Our studies are based on ab initio calculations within the framework of the density functional theory. We determine binding energies of the functionalized carbon nanotubes and the changes in the geometry and electronic structure caused by the functionalization. We observe the characteristic effects such as rehybridization of the bonds induced by fragments attached to carbon nanotubes and pentagon/heptagon (5/7) defects in $-CH_{2}$ functionalized carbon nanotubes. We study also dependence of the binding energies of the functionalized carbon nanotubes on the density of the adsorbed molecules and diameter of the single-wall carbon nanotubes. Our calculations reveal that the $-CH_{2}$ fragments exhibit the strongest cohesion and we determine the critical density of the $-CH_{2}$ fragments which could be adsorbed.
Źródło:
Acta Physica Polonica A; 2009, 116, 5; 841-843
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Advantages of the DFT Augmented Symmetry Approach to Simulations of the Chromium-Based Ring Cr₈ within B3LYP Functional
Autorzy:
Brzostowski, B.
Wojciechowski, M.
Kamieniarz, G.
Powiązania:
https://bibliotekanauki.pl/articles/1030669.pdf
Data publikacji:
2018-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Xx
71.15.Mb
73.22.-f
75.30.Et
31.15.E
Opis:
The DFT estimates of magnetic couplings in molecular nanomagnets are computationally demanding and their values have not achieved the satisfactory accuracy in spite of a lot of effort. We concentrate here on comprehensive tests for predictions of the recently proposed augmented symmetry approach aiming at reducing the computational complexity of the DFT calculations which is particularly important for the Wien2k code. Using the B3LYP functional, we demonstrate the numerical stability of magnetic couplings, magnetic moments and the HOMO-LUMO gaps, changing the fraction of exact exchange α. We reach the significant gain in the computing time without a loss in the accuracy of the final results with respect to those obtained by the standard PBE approach. We conclude that the value α=0.25 leads to best estimation of magnetic couplings for hybrid functionals within Wien2k.
Źródło:
Acta Physica Polonica A; 2018, 133, 3; 591-593
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Derivation of von Weizsäcker Equation Based οn Green-Gauss Theorem
Autorzy:
Romanowski, Z.
Krukowski, S.
Powiązania:
https://bibliotekanauki.pl/articles/1808100.pdf
Data publikacji:
2009-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.15.E-
71.15.Mb
71.15.Dx
Opis:
A simple and short derivation of von Weizsäcker equation for kinetic energy functional is presented. The derivation is based on the Green-Gauss theorem and is valid for one-electron systems. In the proof the asymptotic behavior of wave function for the finite systems was used. Two results important for kinetic energy functional evaluation are also derived as consequences of the Green-Gauss theorem.
Źródło:
Acta Physica Polonica A; 2009, 115, 3; 653-655
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
DFT Estimation of Exchange Coupling Constant of Cr₈ Molecular Ring using the Hybrid Functional B3LYP
Autorzy:
Wojciechowski, M.
Brzostowski, B.
Kamieniarz, G.
Powiązania:
https://bibliotekanauki.pl/articles/1386209.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Xx
71.15.Mb
73.22.-f
75.30.Et
31.15.E-
71.10.-w
Opis:
A study of electronic and magnetic properties of an octametallic chromium-based homonuclear molecule Cr₈F₈(CO₂-C(CH₃)₃)₁₆ is presented, using density functional theory (DFT) approach and linearized augmented plane wave (LAPW) method with Perdew, Burke and Ernzerhof (PBE) and Becke 3-term correlation (B3LYP) functionals. The exchange coupling parameters between transition metals ions are extracted, taking into account two different (ferro- and antiferromagnetic) spin configurations. The value J=3.1 meV found for the hybrid B3LYP functional improves significantly the one obtained for the PBE functional and gives an evidence for the superiority of the former in simulation of molecular nanomgnets. Moreover, the hybrid functional yields excellent spin density localisation, an enhancement of the HOMO-LUMO gaps and the value 2.81 $μ_B$ of magnetic moment at the chromium centre in good agreement with experiment.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 407-409
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Distribution of Zn in Magnetoelectric Y-Type Hexaferrite
Autorzy:
Kouřil, K.
Chlan, V.
Štěpánková, H.
Telfah, A.
Novák, P.
Knížek, K.
Hiraoka, Y.
Kimura, T.
Powiązania:
https://bibliotekanauki.pl/articles/1506927.pdf
Data publikacji:
2010-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.05.Qr
75.85.+t
75.50.Gg
31.15.E-
Opis:
We employ $\text{}^{67}Zn$ NMR to study distribution of $Zn^{2+}$ in cationic sites of magnetoelectric Y-type hexaferrite single crystal, $Ba_{0.5} Sr_{1.5} Zn_2 Fe_{12} O_{22}$. The experimental data are interpreted by comparison with NMR spectra simulated from ab initio calculated hyperfine parameters.
Źródło:
Acta Physica Polonica A; 2010, 118, 5; 732-733
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Exact Exchange Scheme in the Parallel r-Space Implementation of the Kohn-Sham Realization of the Density Functional Theory
Autorzy:
Marchwiany, M.
Birowska, M.
Majewski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1186000.pdf
Data publikacji:
2016-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.15.E-
31.15.-p
61.50.Ah
61.50.Lt
71.15.Mb
Opis:
In this communication, we present the r-space implementation of the Kohn-Sham realization of the density functional theory with the exact exchange functional within the computational algorithm for computers of parallel architecture. In comparison to the standard approach employing the local density functional, the scheme with exact exchange functional requires roughly ten times larger computational burden. The developed parallelization procedure accelerates the computations by a factor of four and six for the exact exchange and the local density functional schemes, respectively. It brings us closer to the treatment of dispersive van der Waals interactions on the fully ab initio level in the large class of systems.
Źródło:
Acta Physica Polonica A; 2016, 130, 5; 1236-1238
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Excited States of Intermolecular Electron-Donor-Acceptor Systems and Internal Geometry of Complex Components
Autorzy:
Deperasińska, I.
Sobieraj, A.
Powiązania:
https://bibliotekanauki.pl/articles/1995340.pdf
Data publikacji:
1999-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.15.Ct
31.70.-f
34.70.+e
Opis:
In this work we present the results of semiempirical AM1 calculations of the energy of electron-donor-acceptor system in the ground and excited states with full optimization of the complex geometry (in terms of both: intermolecular and intramolecular coordinates). A comparison of these results with those obtained for separated acceptor and donor molecules enables the estimation of the energetic effects of changes in internal structure of donor and acceptor which accompany the process of formation and stabilization of excited charge-transfer state. It is shown that energies corresponding to those changes are comparable with the energy of intermolecular interactions between donor and acceptor molecules.
Źródło:
Acta Physica Polonica A; 1999, 95, 3; 309-319
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental and Quantum Chemical Calculations of 2-Amino-4,5,6,7-Tetrahydrobenzo[b]Thiophene-3-Carbonitrile
Autorzy:
Oturak, H.
Kaya Kinaytürk, N.
Topuz, M.
Kutlu, N.
Kaynaker, E.
Talıp, P.
Sert, Y.
Powiązania:
https://bibliotekanauki.pl/articles/1031126.pdf
Data publikacji:
2017-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.15.E-
33.20.Ea
33.20.Tp
33.20.Fb
33.20.Lg
33.20.Bx
Opis:
Vibrational frequencies of 2-Amino-4,5,6,7-Tetrahydrobenzo[b]Thiophene-3-Carbonitrile were calculated using density functional (DFT/B3YLP) method with 6-311++G(d,p) basis set by Gaussian 09. The assignments of the vibrational frequencies have been done by potential energy distribution analysis, using VEDA 4 software. The density functional theory and time dependent density functional theory methods have been used to study the electronic properties of 2-Amino-4,5,6,7-Tetrahydrobenzo[b]Thiophene-3-Carbonitrile. Isotropic chemical shifts were calculated using the gauge-invariant atomic orbital method. All computed spectroscopic properties were compared with experimental ones. The simulated spectra of the molecule show excellent agreement with the experimental spectra.
Źródło:
Acta Physica Polonica A; 2017, 132, 3; 1192-1199
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
First Principles Calculation of ε-Phase of Solid Oxygen
Autorzy:
Kamaruddin, K.
Abedin, A.
Zabidi, N.
Yahya, M.
Taib, M.
Rosli, A.
Powiązania:
https://bibliotekanauki.pl/articles/1398703.pdf
Data publikacji:
2016-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.Pq
74.70.-b
31.15.E-
75.50.Xx
Opis:
The electronic structures of ε-phase of solid oxygen (O₂)₄ are studied within the framework of density-functional theory. The intriguing molecule has been known to have magnetic properties at room temperature by applying pressure. Nevertheless, until now there was no evidence of band structure studied in the antiferromagnetic behaviour of (O₂)₄. We report a comparison study for spin and non-spin polarization orbital which suggests that this ferromagnetic configuration of (O₂)₄ could not be seen experimentally, and antiferromagnetic configuration of (O₂)₄ was seen at higher pressure of about 10 GPa. The antiferromagnetic state transforms into the superconducting state as the sample temperature decreases. The results can serve as a useful approximation in studying general features of the electronic structure. The (O₂)₄ clusters are reported in the Raman study, having significant absorption at 1516 cm¯¹ below infrared region.
Źródło:
Acta Physica Polonica A; 2016, 129, 4; 468-471
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
First Principles Study of Gas Adsorption Dynamics on Pristine and Defected Graphene
Autorzy:
Wlazło, M.
Majewski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1398540.pdf
Data publikacji:
2016-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.15.E-
61.48.Gh
68.43.-h
Opis:
We present the results of ab initio calculations of gas adsorption processes on graphene. Static density functional theory framework is used to obtain adsorption energies of several species on a Stone-Wales defected graphene monolayer. The Van der Waals interaction is taken into account by a semi-empirical correction. Sites closer to the defect are found to induce stronger adsorption compared to sites further away, where the graphene crystal structure is intact. The Car-Parrinello ab initio molecular dynamics simulations are performed at high temperatures. CH₃ is found to be stably physisorbed or chemisorbed at 300 K.
Źródło:
Acta Physica Polonica A; 2016, 129, 1a; A-142-A-144
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
First-Principles Calculations of Structural, Electronic, Optical, and Thermodynamic Properties of CdS, CdTe and Their Ternary Alloys $CdS_{1-x}Te_{x}$ (0.0 ≤ x ≤1.0)
Autorzy:
Ameri, M.
Mesbah, S.
Al-Douri, Y.
Bouhafs, B.
Varshney, D.
Ameri, I.
Powiązania:
https://bibliotekanauki.pl/articles/1364167.pdf
Data publikacji:
2014-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.15.E-
63.20.dk
04.25.-g
78.66.Hf
73.61.At
Opis:
Using first-principle method, we investigate the structural, electronic, optical, and thermodynamic properties of the $CdS_{1-x}Te_x$ semiconductor alloys using generalized gradient approximation for the exchange-correlation potential calculation. The ground state properties are determined for the bulk materials (CdS and CdTe) in cubic phase. Quantities such as the lattice constants and bulk modulus of interest are calculated. Detailed comparisons are made with published experimental and theoretical data and show generally good agreement. The calculated lattice constants scale linearly with composition (Vegard's law). The microscopic origins of the bowing parameter were explained using the contributions from volume deformation, charge transfer and structural relaxation approach. The refractive index and optical dielectric constant for the alloys of interest were calculated by using different models. In addition, the thermodynamic stability of the alloys was investigated by calculating the critical temperatures of alloys.
Źródło:
Acta Physica Polonica A; 2014, 125, 5; 1110-1117
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
First-Principles Study of Structural, Elastic and Mechanical Properties of Zinc-Blende Boron Nitride (B3-BN)
Autorzy:
Daoud, S.
Loucif, K.
Bioud, N.
Lebgaa, N.
Powiązania:
https://bibliotekanauki.pl/articles/1419742.pdf
Data publikacji:
2012-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
45.10.-b
62.20.D-
61.66.-f
62.20.de
81.40.Jj
31.15.E-
Opis:
First principles study of structural, elastic properties and anisotropy effect on the mechanical parameters of the zinc-blende boron nitride has been performed using the pseudopotential plane wave method based on density functional theory with the Teter and Pade exchange-correlation functional of the local density approximation. The equilibrium lattice constant, molecular and crystal densities, bond length, the independent elastic constants, bulk modulus and its pressure derivatives, compressibility, shear modulus, internal strain parameter, isotropy factor, compliance constants, the Debye temperature, Young's modulus, Poisson's ratio, the Lamé constants and sound velocity for directions within the important crystallographic planes of this compound are obtained and analyzed in comparison with the available theoretical data reported in the literature.
Źródło:
Acta Physica Polonica A; 2012, 122, 1; 109-115
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fundamental Gaps in $Cr_{8}$, $Cr_{7}Ni$ and $Cr_{7}Cd$ Molecules
Autorzy:
Brzostowski, B.
Wojciechowski, M.
Kamieniarz, G.
Powiązania:
https://bibliotekanauki.pl/articles/1368520.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.15.Mb
31.15.E-
71.10.-w
Opis:
In this paper we investigate fundamental gaps of three octametallic Cr-based molecular rings $Cr_{8}F_{8}(Piv)_{16}$, $Cr_{7}NiF_{8}(Piv)_{16}$ and $Cr_{7}CdF_{8}(Piv)_{16}$ using the SIESTA package. We find that for the ground-state antiferromagnetic configurations, the gap of the homometallic ring is significantly higher than those of the heterometallic rings. In addition, the HOMO and LUMO orbitals are plotted and discussed.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 234-235
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
H₂ Interaction with rm C₂H₂TM (TM = Sc, Ti, V) Complex Using Quantum Chemical Methods
Autorzy:
Tavhare, P.
Wadnerkar, N.
Kalamse, V.
Chaudhari, Ajay
Powiązania:
https://bibliotekanauki.pl/articles/1398991.pdf
Data publikacji:
2016-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
88.30.R-
31.15.A-
31.15.E-
Opis:
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.
Źródło:
Acta Physica Polonica A; 2016, 129, 6; 1257-1262
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 35

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