Solange Binotto Fagan

Stability investigation and thermal behavior of a hypothetical silicon nanotube

Abstract Even though silicon nanotubes have never been observed, this paper attempts to establish the theoretical similarities and differences between Si and C structures. Through the use of two alternative theoretical approaches, the first principles calculations and empirical potential, the electronic and structural properties of this hypothetical material are examined. The first principles calculations are based on the density-functional theory and it is shown that depending on their chiralities and diameters, the silicon nanotubes may present metallic (armchair) or semiconductor (zigzag and mixed) behaviors, similar to carbon structures. It is shown that the gap decreases in inverse proportion to the diameter, thus approaching zero for planar graphite, as was expected. In the second alternative approach, the Monte Carlo simulations are used with the Tersoffs empirical potential to present a systematic study on the thermal behavior of these new structures. It is shown that similarities like band structures and density of states are observed between the C and Si nanotubes. Nevertheless, there are relevant discrepancies in the thermal stabilities and energy differences between the cohesive energies per atom for the two tubes, compared with the corresponding bulks, implying the very improbable structure of the silicon nanotubes.

Electronic and magnetic properties of iron chains on carbon nanotubes

In this work the structural, electronic and magnetic properties of one-dimensional Fe chains interacting with a semiconductor single-wall carbon nanotube are investigated using first-principles spin-polarized calculations. A systematic study of several configurations of a Fe wire interacting with a nanotube both from outside as well as inside is presented, and the resulting equilibrium distances, binding energies and magnetizations are discussed. The most stable configurations are compared with previous results obtained for a single Fe atom interacting with the tube.

Ab initio study of an organic molecule interacting with a silicon-doped carbon nanotube

Abstract The electronic structure of an organic molecule interacting with a Si-doped single-wall carbon nanotube is studied through first principles calculations based on density functional theory. The silicon substitutional doping on (10, 0) semiconductor carbon nanotube introduces an empty level in the gap. Differently to the weak physisorption resulting of direct interaction of an organic molecule to the tube surface, the binding energy of the molecule through the Si-site is shown to be much stronger. The band structure for the resulting system presents one half-filled level in the gap. A study of one particular single organic molecule (S 2 C 6 H 5 ) connected to the tube through a Si-site is presented.

Energetics and structural properties of adsorbed atoms and molecules on silicon-doped carbon nanotubes

Abstract The energetics and structural properties of atoms and molecules on a substitutional Si atom in single wall carbon nanotubes (SWCN) are investigated using first principle calculations based on density-functional theory. A detailed analysis is performed for the geometry and the electronic structures of a Si-doped semiconducting (10,0) carbon nanotube interacting with F, Cl, H, CH3, and SiH3. A common feature for the systems with these atoms or molecules is the presence of one half-filled level close to the top of the valence band. The specific position of this level in the gap depends on the chemisorbed species and the binding energy between this species and the Si atom.

First Principles Study of Transverse Electric Fields on Carbon Nanotubes

This paper presents the electronic charge density modifications due to the effects of the transverse uniform electric fields applied on the semiconductor and metallic single wall carbon nanotubes. The results obtained, by means of density functional calculations, show that semiconductor and metallic nanotubes have different behavior in the presence of the transverse electric field: the first present the electronic charge polarized due to the local orbital localization, while the metallic species are polarized due to charge dislocation throughout the surface.

Ab Initio Study of Si Doped Carbon Nanotubes: Electronic and Structural Properties

Abstract : We report the electronic and structural properties of silicon doped carbon nanotubes using first principles calculations based on the density-functional theory. In the doped metallic nanotube a resonant state appears about 0.7 eV above the Fermi level and for the semiconductor tube the Si introduces an empty level at approximately 0.6 eV above the top of the valence band.

DESENVOLVIMENTO E AVALIAÇÃO DE UM OBJETO DE APRENDIZAGEM SOBRE O CUSTO DO BANHO PARA ENSINO DE FÍSICA

Este trabalho apresenta as experiencias obtidas por docentes e discentes da UNIFRA na producao e aplicacao de objetos de aprendizagem interativos desenvolvidos segundo a metodologia RIVED, Rede Interativa Virtual de Educacao, para a area de fisica. O material didatico “Custo do Banho” foi desenvolvido com recursos pedagogicos, de conteudo e de tecnologias multimidias e tem demonstrado ser uma ferramenta interessante para subsidiar o entendimento de quantidades fisicas como vazao e potencia eletrica calculando o custo de um banho.

Encapsulation of Metallocenes in Single‐Wall Carbon Nanotubes: an Ab Initio Study

In this work we study the electronic, magnetic and structural properties of cobaltocene molecule (bis‐cyclopentadienyl cobalt) interacting with (13, 0) semiconductor single‐wall carbon nanotubes through ab initio simulations. The calculations are based on the first principles spin‐polarized density functional theory, using numerical atomic orbitals as basis set implemented in the SIESTA code. Our calculations indicated that the cobaltocene molecule inside the SWNT behave as electron donor thus charging the electronic bands of the nanotube and increasing its Fermi energy due to the molecule‐nanotube interaction.