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Ab Initio Study of Functionalized Carbon Nanotubes

100%
Milowska K., Birowska M., Majewski J.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
841-843
EN
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.
2
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Van Der Waals Density Functionals for Graphene Layers and Graphite

100%
Birowska M., Milowska K., Majewski J.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
845-848
EN
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.
3
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Structural and Electronic Properties of Functionalized Graphene

100%
Milowska K., Birowska M., Majewski J.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
842-844
EN
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.
4
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Ab Initio Modeling of Graphene Functionalized with Boron and Nitrogen

100%
Woińska M., Milowska K., Majewski J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1087-1089
EN
We investigate theoretically the electronic properties of graphene functionalized with nitrogen and boron atoms substituted into the graphene monolayer. Our study is based on the ab initio calculations in the framework of the density functional theory. We predict the dependence of the energy band gap, binding energy per atom, and the shift of the Fermi level on the concentration of dopants. Moreover, we examine the influence of the distribution of B/N atoms on the specified properties.
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