Estudo de novos nanomateriais por primeiros princípios: confinamento de oxigênio em nanotubos, camadas de AgSH, Ag2S e filmes finos ferroelétricos

Abstract

In this thesis, we employed first principles calculations based on the Density Functional Theory to investigate proposals of novel nanostru tured compounds. We have treated three distinct problems. In a rst work, we investigated the en apsulation of O2 mole ules within fullerenes and narrow nanotubes. We showed the self-assembly of these mole ules in lusters, and the alignement of su h lusters along the nanotube axis, forming linear hains. We hara terized su h stru tures and we ondu ted mole ular dynami s simulations to perform stability tests. The se ond one is related to two dimensional stru tures. Re ently, materials su h as MoS2 and other di hal ogenides have attra ted great attention due to their physi al properties and their potential of appli ation in nanote hnology. Following this trend, and motivated by some experimental results, we proposed materials with stoi hiometries Ag2X and AgXH, in whi h X is a hal ogenide element, su h as sulfur or selenium. We determined the ele troni and stru tural properties of mono and multilayers based on these ompounds. We dis ussed their stabilities, and we hara terized them, showing the existen e of dire t energy gaps whi h are strongly dependent on the number of layers. In some ases, we showed the o urren e of semi ondu tor-metal transitions. Finally, we investigated barium oxide (BaO) thin lms. Motivated by works whi h indi ate the possibility of modulations of polarization properties as a fun tion of ompressive deformations, we ondu ted studies of this phenomenology in ultra thin lms. We also hara terized the surfa e re onstru tion of the lms when fun tionalized with hydroxyl groups.