Banca de DEFESA: DAYVISON WEBER MAIA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE: DAYVISON WEBER MAIA
DATA: 23/02/2026
HORA: 09:00
LOCAL: Híbrida
TÍTULO: PROPRIEDADES FÍSICAS DE NANOFITAS DE CARBONO FORMADAS POR ÁTOMOS COM HIBRIDIZAÇÕES sp 2 e sp 3 .
PALAVRAS-CHAVES: Nanocarbonos, Propriedades Eletrônicas, Teoria do Funcional da Densidade, Nanofitas de Me-grafeno, Nanofitas de Ph-grafeno, Estados magnéticos.
PÁGINAS: 138
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Física
RESUMO:

The physical and chemical properties of nanocarbons have attracted the
scientific community’s attention in the last decades. Computational and
theoretical investigations have been indispensable and relevant in the
development of research on these systems. In this context, this thesis presents
a study of the structural, electronic, and magnetic properties of one-dimensional
physical systems conceived via 2D carbon allotropes, recently proposed in the
literature. The me-graphene and ph-graphene are physical systems that present
atoms with hybridized sp 2 and sp 3 states. These structural properties originate a
thickness of angstrom order, differently from atomic thickness associated with
the graphene, characterizing these systems like quasi-2D materials. Through
different chiralities and structural details of edges, nanoribbons were proposed
for each one of these systems. The calculations were developed via density
functional theory (DFT), using the SIESTA computational package. With relation
to the me-graphene nanoribbons (MeGNRs), the results demonstrate that the
confinement and edge effects perform an important role in the investigated
properties. In particular, differently from 2D systems, which are semiconductors
of indirect energy gap, the nanoribbons can display semiconductor behavior of
direct or indirect energy gap, in addition to one of the cases presenting metallic
behavior, exhibiting a low dispersive band around the Fermi level. This last case
shows spin-dependent properties, revealing a phase transition of metal –
semiconductor type between not polarized and polarized states. The ph-
graphene nanoribbons (PHGNRs) can exhibit semiconductor and metallic
electronic behaviors. Once again, confinement and edge effects are crucial to
characterize these systems, which exhibit multiple magnetic states defined by
the spin orientation, which mostly is distributed in the internal atoms of the
structure. In this sense, the energetic stabilization mechanism that occurs from
spin polarization is provenient of internal states of the ribbon, differently from
other systems in the literature, whose central agents are edge atoms.
Therefore, in the PHGNRs case, it was demonstrated that edge effects are
secondary in the electronic and magnetic definitions of the resultant systems,
which made these materials promising for nanoelectronic applications, given
that the synthesis precision in the edge region is not that relevant to the result
properties. Finally, in both cases, it is possible to modulate the system’s
properties by the confinement and edge effects and magnetic ordering of states,
allowing a variety of electronic behaviors and some other characteristics, like
the band profiles and modulation of energy gap, among others.

MEMBROS DA BANCA:
Externo à Instituição - 638.***.***-78 - ANDREA BRITO LATGE - UFF
Presidente - 1548848 - EDUARDO COSTA GIRAO
Externo ao Programa - 024.***.***-17 - FABRÍCIO MORAIS DE VASCONCELOS - UFC
Externo ao Programa - 1689475 - JONATHAN DA ROCHA MARTINS
Interno - 423297 - JOSE PIMENTEL DE LIMA
Externo à Instituição - 044.***.***-86 - MARCELO LOPES PEREIRA JÚNIOR - UnB