https://doi.org/10.1140/epjd/s10053-023-00729-y
Regular Article – Clusters and Nanostructures
DFTB study of energetic and structural properties of nano-onions with point defects in their structure
Instituto Superior de Tecnologías y Ciencias Aplicadas (InSTEC), Universidad de La Habana, Ave. Salvador Allende, No. 1110, e/ Ave. Rancho Boyeros y Czda. Infanta, Quinta de los Molinos. Plaza de la Revolución, 10400, La Habana, Cuba
Received:
30
April
2023
Accepted:
6
July
2023
Published online:
4
August
2023
Since the experimental works published by Ugarte in 1993, nested almost perfect graphitic spheres have been generated in the condensed phase by irradiation with high-energy electrons of graphitic particles. The quasi-spherical shapes of these molecular systems were more marked than those obtained by Ijima by applying the arc-discharge method to amorphous carbon films. Although Ugarte was able to describe the influence of parameters such as temperature and dose of electronic radiation on the transformation of these structures, theoretically it has not been possible to explain the causes of the triggering of the above-mentioned process because of the complexity of these systems. Using a computational method based on density functional theory with tight-binding approximation (DFTB), the geometries of fullerenes of order 
(2160 atoms) and carbon nano-onions (CNOs) of up to five layers were optimized, and the different energetic and geometric parameters of fullerenes and polyhedral CNOs were calculated. By introducing in the structure of these nanomaterials the point defects that are commonly produced during their irradiation (monovacancies, divacancies, and Stone–Wales), the possible structural deformations caused in these arrangements, as well as the formation energies were analyzed. The results obtained allow us to verify that 
divacancies can modify the outermost nano-onion layers with an effect similar to that described experimentally by Ugarte.
Supplementary Information The online version contains supplementary material available at https://doi.org/10.1140/epjd/s10053-023-00729-y.
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