title: Defects in graphene-based twisted nanoribbons: structural, electronic, and optical properties.
abstract: We present some computational simulations of graphene-based nanoribbons with a number of half-twists varying from 0 to 4 and two types of defects obtained by removing a single carbon atom from two different sites. Optimized geometries are found by using a mix of classical quantum semiempirical computations. According with the simulations results, the local curvature of the nanoribbons increases at the defect sites, especially for a higher number of half-twists. The HOMO-LUMO energy gap of the nanostructures has significant variation when the number of half-twists increases for the defective nanoribbons. At the quantum semiempirical level, the first optically active transitions and oscillator strengths are calculated using the full configuration interaction (CI) framework, and the optical absorption in the UV/vis range (electronic transitions) and in the infrared (vibrational transitions) are achieved. Distinct nanoribbons show unique spectral signatures in the UV/vis range, with the first absorption peaks in wavelengths ranging from the orange to the violet. Strong absorption is observed in the ultraviolet region, although differences in their infrared spectra are hardly discernible.
authors.affiliation: Centro Federal de Educação Tecnológica do Ceará, Avenida 13 de Maio, 2081, Benfica, 60040-531 Fortaleza, Ceará, Brazil.
authors.forename: E W S
authors.initials: EW
authors.lastname: Caetano
authors.forename: V N
authors.initials: VN
authors.lastname: Freire
authors.forename: S G
authors.initials: SG
authors.lastname: dos Santos
authors.forename: E L
authors.initials: EL
authors.lastname: Albuquerque
authors.forename: D S
authors.initials: DS
authors.lastname: Galvão
authors.forename: F
authors.initials: F
authors.lastname: Sato