Energy stability and electronic properties of carbon nanotorus at a localized breaking of interatomic bonds: computer modeling

This paper is devoted to the study of the dynamic processes that occur in the carbon nanotorus during localized breaking of interatomic bonds, and to the analysis of the influence of these processes on the electronic properties of carbon nanotorus. The object of research is a carbon nanotorus with chirality indices (13, 0) with a diameter of 20 nm and a thickness of 1 nm obtained as a result of defect-free folding of a zigzag carbon nanotube of appropriate geometric dimensions into a ring. The behavior of the nanotorus is modeled by the molecular dynamics method using a modified Brenner potential to describe the interaction between atoms. It is shown that over time, the nanotorus straightens into a nanotube, while maintaining energy stability. It is found that the process of nanotorus straightening is accompanied by the appearance of deformation wave-like bends propagating at a speed of 200 m/s along the atomic network of the structure. These bends lead to deformation of the nanotorus and numerous local breaks in the bonds between atoms. However, broken bonds are restored within a few femtoseconds before the structure relaxes in energy, therefore, in general, the atomic framework of the nanotorus remains defect-free after rectification. The results of calculating the distribution of the density of electronic states (DOS) of a nanotorus by the self-consistent charge density functional tight-binding (SCC-DFTB) quantum method showed that at the moment of localized breaking of interatomic bonds around the circumference of the tubular framework, the nanotorus loses its semiconductor properties, becoming a gapless conductor. The discovered physical phenomenon explains the process of nanotorus formation during synthesis accompanied by multiple ruptures of the nanotori and reverse closure of the nanotubes into the nanotori.