Reactive molecular dynamics of nanostructured systems

Author(s)

José Moreira de Sousa

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Física Gleb Wataghin
• Defense date: 2016-03-18

Examining board members

Douglas Soares Galvão; Mario Antonio Bernal Rodriguez; Mário Noboru Tamashiro; Eduardo Costa Girão; Ricardo Paupitz Barbosa dos Santos

• Advisor: Douglas Soares Galvão

Abstract

Carbon nanotechnology revolution created a new era in materials science. The goal is the sustained development of new materials with superior physical and chemical properties than the existing ones. Therefore nanostructures formed by the carbon atoms has been intensively studied over the last decades, such as fullerenes, carbon nanotubes and more recently graphene. Graphene is a 2D nanostructure composed of hybridized carbon atoms sp² in compact hexagonal shape whith the thickness of a carbon atom. Graphene, in addition of being strong is light, almost transparent and an excellent conductor of heat and electricity. However it is a zero band gap material which limits its use in some electronic devices. Thus, there are new searches for new nanomaterials with the same characteristics or better than graphene, but with semiconducting properties. New better than nanomaterials like Silicene, carbon nitride and graphene-like nanostructures (nanotubes based on graphynes) among others have received extensive attention in theoretical and experimental research. From a theoretical point of view, several computational methods have been used to study the physical and chemical properties of nanostructures. Computer simulations of molecular systems are extremely importance as they help us in the interpretation of experimental results, for through these methods we have access to structural, electronic and dynamic states. These methods can be treated from first principles (quantum mechanics), or through of the force fields applied in classical methods. Using these methodologies with the use of a modern force fields we have studied the structural, mechanical properties, fracture patterns and degradation into gaseous atmospheres of nanostructured systems composed of carbon, nitrogen and hydrogen atoms. In the study of degradation in gaseous atmospheres we performed a dynamic study exposing carbon nanotubes under mechanical twisting and graphdiynes membranes in gaseous atmospheres consisting of hydrogen atoms. For carbon nanotubes with mechanical twists, our results show that from the reactive curvatures on the tube walls can obtain nanoribbons of graphene via fractures in these regions by the incorporation of reactive hydrogen atoms. For graphdiynes our results show that the hydrogen incorporated atoms bonded have different rates and that these rates change in complex patterns. In the mechanical study of nanostructured systems we calculate the torsional mechanics of the nanotubes based on graphynes where we obtain that these nanotubes are more elastic than standard carbon nanotubes when compared to the values of angles of the fracture twist. Finally, we investigated the mechanical properties of nanostructures formed by carbon and nitrogen atoms fracture patterns (g-CN, Triazine-based g-C3N4 and Heptazine-based g-C3N4) where our results show that due to the presence of pores and single chemical bonds between carbon and nitrogen atoms (CN) we obtain different and unique fracture patterns (AU)

• FAPESP's process: 12/20901-0 - Structural, Mechanical and Transport Properties of Nanostructures Formed of Carbon and Nitrogen Atoms
• Grantee: José Moreira de Sousa
• Support Opportunities: Scholarships in Brazil - Doctorate