Estudo das propriedades optoeletrônicas e vibracionais das estruturas do PhaBN e dos nanocones de carbono usando cálculos de DFT

Abstract

Recently, a flat structure similar to graphene, Phagraphene, was discovered through a theoretical study. Its formation is composed of three types of carbon rings (pentagons, hexagons and heptagons), presenting several electronic properties. However, there is no theoretical investigation of the properties of this structure formed by boron and nitrogen the materials made of carbon are usually metallic. The simulations were performed with the objective of comparing the results of all the structures. Atoms, the phaBN. In addition, many studies have been done on structures formed by carbon nanocons with disclination angles 60°; 120° e 180°, but there are few studies in the literature on hourglass-shaped double cones, enabling the discovery of new properties. The present dissertation is within the scope of Nanoscience, and aims to study the nanostructures of phaBN and nanocones in the form of hourglass, by means of computational modeling of rst principles implemented in the CASTEP and DMol3 codes to optimize the structures, with the objective of nding the conformation of lower energy, which is the most stable. Subsequently, we investigated the optoelectronic, vibrational and thermodynamic properties of phaBN, and for the fifteen structures formed by the carbon cones, only the electronic properties were presented. The study of these properties was performed by means of quantum calculations through the theory of density functional (DFT), using the approximation of the generalized gradient-GGA. Through our calculations, we observed that the band structure and state density of phaBN have a gap of 2,739 eV which is about 2 eV less than the hexagonal structure of boron nitride h-BN, thus being a semiconducting material of long gap. By means of the optical, vibrational and thermodynamic properties it was possible to observe the absorption interval, the stability of the structure and its formation process, respectively. We also observed that all the carbon nanocones are metallic when we do the analysis of the density of electronic states, a result already expected since the materials made of carbon are usually metallic. The simulations were performed with the objective of comparing the results of all the structures.