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Wyświetlanie 1-6 z 6
Tytuł:
Structural and Electronic Properties of Functionalized Graphene
Autorzy:
Milowska, K.
Birowska, M.
Majewski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1492822.pdf
Data publikacji:
2011-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.15.E-
61.46.-w
73.20.At
73.22.-f
Opis:
In the present paper, we study the effects of functionalization of graphene with simple organic molecules OH, and $NH_2$, focusing on the stability and band gaps of the structures. We have performed DFT calculations for graphene supercells with various numbers of the attached molecules. We have determined adsorption energies of the functionalized graphene mono- and bilayers, the changes in the geometry, and the band structure. We observe the characteristic effects such as rehybridization of the bonds induced by fragments attached to graphene and opening of the graphene band gap by functionalization. We have also studied the dependence of the adsorption energies of the functionalized graphene on the density of the adsorbed molecules. Our calculations reveal that the -OH and $-NH_2$ groups exhibit the strong cohesion to graphene layers. Further, we determine the critical density of the OH fragments which lead to the opening of the band gap. We also show how to engineer the magnitude of the band gap by functionalizing graphene with $NH_2$ groups of various concentrations.
Źródło:
Acta Physica Polonica A; 2011, 120, 5; 842-844
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Van Der Waals Density Functionals for Graphene Layers and Graphite
Autorzy:
Birowska, M.
Milowska, K.
Majewski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1492823.pdf
Data publikacji:
2011-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.15.E-
61.46.-w
73.20.At
73.22.-f
Opis:
In this communication, we present results of theoretical studies of various systems where Van der Waals interaction plays a considerable role. In the first-principle calculations performed in the density functional theory framework we implement novel functionals accounting for Van der Waals forces and employ to the test cases of graphite and graphene layers. It turns out that this approach provides a solution to the long standing problem of overbinding between graphene layers in bulk graphite, giving the distance between the carbon layers in excellent agreement with experiment. In graphene bilayers, Van der Waals functionals lead to energetic barriers for A-B to A-A ordering of graphene bilayers that are by a factor of two smaller than the barriers obtained with standard functionals. It may be of crucial importance, particularly, if one uses atomistic ab initio methods as a starting point for multi-scale modeling of materials and for determination of effective potentials.
Źródło:
Acta Physica Polonica A; 2011, 120, 5; 845-848
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Study of Magnetic Molecules Containing Cr₉ Chromium-Based Rings within Density Functional Theory
Autorzy:
Brzostowski, B.
Wojciechowski, M.
Kamieniarz, G.
Powiązania:
https://bibliotekanauki.pl/articles/1032265.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Xx
71.15.Mb
73.22.-f
75.30.Et
31.15.E-
Opis:
We examine the electronic and magnetic properties of three frustrated Cr₉ molecules with a single bond defect using density functional theory method. Five non-equivalent broken-symmetry spin configurations with S=±3/2 for Cr are considered, the corresponding differences between the total energies are calculated and the exchange interaction parameters J extracted using different scenarios. We find that the couplings for all molecules are antiferrimagnetic. We also estimate the fundamental gaps and in addition, the high occupied molecular orbitals and low occupied molecular orbitals are plotted and discussed.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 961-963
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:
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:
Mapping of the DFT Spin Configuration Energies of Cr8Cd Molecular Ring onto the Energy Structure of Falicov-Kimball Model
Autorzy:
Wojciechowski, M.
Brzostowski, B.
Lemański, R.
Kamieniarz, G.
Powiązania:
https://bibliotekanauki.pl/articles/1386266.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 comprehensive study of electronic and magnetic properties of a recently synthesized nonametalic chromium-based heteronuclear molecule Cr₈CdF₉(O₂C-C(CH₃)₃)₁₈ is presented, using DFT and Falicov-Kimball (FK) model approach. The magnetic moments are calculated and the spin charge density map is discussed. The exchange coupling parameters between transition metals ions are extracted, taking into account all the nonequivalent spin configurations. It is demonstrated that the energies of the spin configurations can be reproduced by the FK model with a set of parameters consistent with that for the parent Cr8 molecule. For molecular ring considered, the ground state corresponds to the antiferromagnetic configuration and the ferromagnetic configuration yields the highest energy.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 410-412
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-6 z 6

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