Estudo da Adsorção de Moléculas Diatômicas (CO, NO e SO) sobre Nanoclusters de Níquel via Teoria do Funcional da Densidade

Abstract

In this master dissertation a theoretical study was carried out on the adsorption of dia tomic molecules (CO, NO and SO) on nickel nanoclusters via density functional theory (DFT). This study focuses on the understanding of energetic stabilization, structural pat terns and changes in magnetic properties in relation to the size of nickel nanoclusters (2 to 15 atoms), involved in the molecular adsorption process. First of all, we performed the convergence tests in order to adjust the methodology to be used. Next, an ab initio study was done to optimize the most stable structures for the nickel nanoclusters, N in (n = 2 - 15 atoms). To improve the understanding about the energetic stability of these systems was calculated the stability function (∆2E), which highlighted two systems as being more stable and thus possible candidates to serve as substrate in the adsorption of molecules, which are N i6 and N i10. In order to better understand how this system behaves in a che mical environment, it was then performed the adsorption of the three diatomic molecules where we identified that the CO molecule has preference to adsorb on the top site for both systems, the NO molecule adsorbed on top and bridge on N i6 and N i10 respectively while the SO molecule adsorbed to both systems on hollow. All these calculations were performed with PBE and PBE + vdW functionals and some of the main properties of these systems were calculated as structural, energetic and magnetic properties.