Estudo teórico das propriedades eletrônicas, ópticas, vibracionais e termodinâmicas de monocamadas de TMDs do Tipo OsX2 (X = S, Se, Te) usando o formalismo DFT.

Abstract

Transition Metal Dichalcogenides (TMDs) are materials formed by the junction of chalcogen with a transition metal and that gained prominence for being two-dimensional materials, as well as graphene. This peculiarity of some TMDs presenting a two-dimensional structure is due to the fact that these materials have a lamellar structure and are formed by layers. Some of the most studied TMDs showed properties as promising as those presented by other materials widely used in the manufacture of the most diverse types of technological devices, which aroused the interest in extensively studying other TMDs. Thus, in this work we will study the TMDs formed by the chalcogens Sulfur (S), Selenium (Se) and Tellurium (Te) together with the transition metal Osmium (Os), that is, TMDs of the type OsX2, with X representing the chalcogens. The Density Functional Theory (DFT) was used to obtain the geometric, electronic, optical, vibrational and thermodynamic properties of monolayers of these materials. The exchange and correlation functionals GGA-PBE and LDA-CAPZ were used to obtain these properties, whose calculations were performed using the CASTEP code, which contains an implementation of the DFT theory with a plane wave basis. The results of the properties were shown in graphs of band structure, dielectric function, optical absorption, phonon dispersion, thermodynamic potentials, thermal capacity and Debye temperature of the TMDs. These results showed, among other things, that the structures for the three TMDs (OsS2, OsSe2 and OsTe2) were stabilized and that these present semiconductor properties, since the materials presented gaps of energy that ranged from 0.232 eV of OsTe2 to 1.160 eV of OsS2. Furthermore, the results showed that the synthesis of these materials can be achieved spontaneously.