Banca de QUALIFICAÇÃO: SIDNEY MARQUES GUEDES DOS SANTOS

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
DISCENTE: SIDNEY MARQUES GUEDES DOS SANTOS
DATA: 27/08/2025
HORA: 16:00
LOCAL: Remota (On-line)
TÍTULO: SIMULAÇÕES COMPUTACIONAIS DE SISTEMAS HÍBRIDOS CnH2@SWCNT: CADEIAS LINEARES DE CARBONO CONFINADAS EM NANOTUBOS DE CARBONO DE PAREDE SIMPLES SOB A INFLUÊNCIA DE UM CAMPO ELÉTRICO EXTERNO
PALAVRAS-CHAVES: Nanotubos de carbono, Carbinas, Poliinas, Campo elétrico, DFT
PÁGINAS: 65
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Física
RESUMO:

In this work, we present a theoretical study based on density functional theory
(DFT) simulations of hybrid systems consisting of linear carbon chains saturated with
hydrogen (Cn H2 ) confined inside single-walled carbon nanotubes (SWCNTs) of zig-zag
(8,0) and armchair (5,5) types, under the influence of a transverse external electric field.
The main objective was to investigate how the electric field modifies the structural and
electronic properties of these systems, especially the bond length alternation (BLA), the
transverse deformation of the tube, and the charge transfer to the confined chain, using
different analysis methods (Mulliken, Voronoi, and Hirshfeld). The results show that, for
(8,0) nanotubes, the applied field induces significant ovalization, greater charge

redistribution, and a pronounced reduction in BLA, with a tendency toward a cumulene-
like transition in longer chains. In contrast, armchair (5,5) nanotubes exhibit milder

changes, indicating higher structural rigidity and preservation of the polyyne character.
The analysis of the electronic band structure revealed that (8,0)-based systems display
electronic hysteresis after field removal, while (5,5) systems almost entirely recover their

original profile. Finally, a quantitative comparison was made between the results under
electric field and literature data for axial strain, highlighting marked differences in
structural instability mechanisms and charge transfer. These findings underscore the
importance of nanotube topology and the type of external stimulus in controlling the
physicochemical properties of Cn H2 @SWCNT hybrid systems, with potential applications
in nanoelectronic devices.In this work, we present a theoretical study based on density
functional theory (DFT) simulations of hybrid systems consisting of linear carbon chains
saturated with hydrogen (CnH2 ) confined inside single-walled carbon nanotubes
(SWCNTs) of zig-zag (8,0) and armchair (5,5) types, under the influence of a transverse
external electric field. The main objective was to investigate how the electric field modifies
the structural and electronic properties of these systems, especially the bond length
alternation (BLA), the transverse deformation of the tube, and the charge transfer to the
confined chain, using different analysis methods (Mulliken, Voronoi, and Hirshfeld). The
results show that, for (8,0) nanotubes, the applied field induces significant ovalization,
greater charge redistribution, and a pronounced reduction in BLA, with a tendency toward
a cumulene-like transition in longer chains. In contrast, armchair (5,5) nanotubes exhibit
milder changes, indicating higher structural rigidity and preservation of the polyyne
character. The analysis of the electronic band structure revealed that (8,0)-based systems
display electronic hysteresis after field removal, while (5,5) systems almost entirely recover
their original profile. Finally, a quantitative comparison was made between the results
under electric field and literature data for axial strain, highlighting marked differences in
structural instability mechanisms and charge transfer. These findings underscore the
importance of nanotube topology and the type of external stimulus in controlling the
physicochemical properties of Cn H2 @SWCNT hybrid systems, with potential applications
in nanoelectronic devices.

MEMBROS DA BANCA:
Interno - 1548848 - EDUARDO COSTA GIRAO
Interno - 3374421 - LUCAS SOARES MARINHO
Interno - 1250015 - PALOMA VIEIRA DA SILVA
Presidente - 1340442 - RAMON SAMPAIO FERREIRA