Estudos de propriedades eletrônicas e estruturais de nanoestruturas tubulares com estequiometria BxCyNz selecionadas

Abstract

In these days there is a growing scientific interest in boron (B), carbon (C), and nitrogen (N) composites due to their aplicability potential to be used as active parts in electronic nanoscale devices. The great structural similarities between graphite and hexagonal boron nitride have motivated the synthesis of B x C y N structures, with the expectation that the electronic properties of these new materials are intermediate if compared to the isolated compounds. Besides, it is expected that the mechanical properties of these systems are similar to those presented by the superhard cubic C and BN. In these work we have investigated the structural, energetic and electronic properties of B x C y N z z nanotubes (formed by the connection of intercalated C and BN stripes along the tubes axis) through first-principles calculations. Our goal is to observe deformations at the tubular structures of the systems, order of importance of stability determining factors (diameter, number and type of chemical bonds, and structure deformation), and alterations at the electronic structure for the studied systems. We have performed calculations for the zigzag (10,0), (20,0), (30,0) e (40,0) and armchair (10,10), (20,20), (30,30) e (40,40) BC N stoichiometry. Also, for the (10,0) and (10,10) tubes, we have studied the BC e B 2 CN stoichiometries. It was seen that greater deformation occurred for the tubes with smaller diameters. For this case the distance between opposite C stripes is smaller than the observed for the BN ones. However, with the diameter increasing it was observed a reversion of this behavior, with the BN stripes closer to each other, if compared to the C ones. Through the energetic analysis, it was observed that the increase in the BN concentration contributes to a higher stability. Also, it was seen that the stability increases as the diameter increases, with a saturation for the energy values for tubes armchair with diameters equal or larger than 40,69 2 with diameters equal or larger than 31,32 ˚ A. Finally, the deformation effect for smaller tubes contributes to increase the stability of these systems. The electronic analysis showed us that the armchair BC N tubes are metallic for all studied diameters, while the zigzag ones presented small energy gaps between 0.2 and 0.4 eV. For the other stoichiometries it was seen that the armchair tubes energy gap depends exclusively of the system composition, increasing with the increasing in the BN concentration. On the other hand, for the zigzag ones it was observed a constant energy gap of 1.2 eV for all studied stoichiometries, except for the BC 8 N with a gap of 0.4 eV.