Simulação computacional aplicada à sistemas 2D: tricloretos de metais de transição em grafeno e funcionalização de eletrenos

Abstract

The discovery of graphene boosted the study of 2D materials, considering that these materials have wide applicability in the development of nanodevices. This makes computer simulation a platform for predicting new materials and can even offer experimental directions. Therefore, this work has an interest in using the Density Functional Theory to investigate the functionalization of electrenes through the oxidation and formation of lateral heterostructures, and the transition metal trichlorides, RuCl3 and OsCl3 , and their heterostructures Van der Waals with graphene. First, we analyzed the oxidation process on the monolayer and bilayer of an electrenes set, in which the stability structural is preserved only for the nitrides of Ca, Sr, and Ba, and the Y2C. A structural transition is observed from hexagonal to tetragonal forming structures as (AOAN)t and O(AN)2AO)t, for A= Ca, Sr and Ba, that can be captured with XANES simulations. The spin-polarized band structure reveals a formation of half-metal states localized in the Nitrogen atoms with a magnetic moment of ∼ 1μ B . Therefore, these systems are characterized by spin-polarized channels in the AN layers protected by AO oxidized layers. Following the study of electrenes and knowing that the hydrogenation and fluorination process of Ca 2 N induce mangnet moment localized in the Nitrogen atoms with the formation of half-metal states, we propose the formation of lateral structures formed by primitive Ca2N intercalated by hydrogenated (fluorinated) Ca2N. We notice a charge transfer from primitive regions to hydrogenated (fluorinated) regions, in which most part of the charge is received by the Nitrogen atoms nearest the interface. The spin-polarized band structure and the spin density reveal the formations of NFE states with 1D confinement in the primitive regions intercalated by magnetic moment localized in the Nitrogen atoms. The transmission probability and electronic current reinforce the presence of spin-polarized transport in the perpendicular direction of the hydrogenated (fluorinated) regions. Finally, following the DFT+U+SOC approach, we studied the consequences of the presence of graphene (Gr) in the Ruthenium and Osmium trichlorides, RuCl3 and OsCl3. The work function differences between these systems induce a charge transfer from the Gr to RuCl3 and OsCl3 of the order of 10^13 e/cm2 that is distributed in a way no-homogeneous. Analyzing the electronic properties, the isolated systems are Mott insulators, however, with the graphene presence, the charges transferred occupy the Ru-4d and Os-5d states leaving a metallic character. The occupancy of these states can be manipulated by the application of an external electric field, in such a way can control a metal-insulator. We found a zigzag antiferromagnetic (ZZ-AFM) and ferromagnetic (FM) ground state phase with magnetization easy axis out-of-plane and in-plane for the RuCl3 and OsCl3, respectively. In the graphene presence, the ZZ-AFM phase and the magnetization easy axis of RuCl3 are preserved. In contrast, the OsCl3 changes the ground state magnetization from FM to ZZ-AFM with the graphene presence, but the in-plane easy axis is preserved. Our results show that charge doping and the application of an external electric field can control the magnetic anisotropy energies. Therefore, this Thesis shows two types of materials that through interaction with other elements and the formations of heterostructures become interesting platforms for applications in spintronics devices.