Propriedades eletrônicas, estruturais e espectroscópicas do Bulk e superfícies do BaSnO3 modelados computacionalmente por teoria de funcional de densidade.

Tin-based Perovskites are promising materials due to their physical and chemical properties that are governed by the electronic and structural characteristics of the bulk and their respective surfaces. Such properties allow BaSnO3 (BSO) to be applied as gas sensor, photocatalyst, transparent optical conductor, among other applications. Experimental studies have revealed that the cubic structure of BSO correspond to the thermodynamic ground state. However, tin-based perovskites may adopt polymorphic structures such as tetragonal, rhombohedral and orthorhombic. In this sense, the main aim of this work is the theoretical study of the main properties of BSO in the cubic phase applying the Density Functional Theory, taking into account the influence of the applied methodology in the property’s description. Besides the cubic structure, the polymorphic phases of BSO were evaluated under high pressure (0 to 30 Gpa), aiming to investigate the possibility to obtain other BSO phases. The Murnaghan, Birch-Murnaghan, Poirier-Tarantola and Vinet equations of state (EOS) were used to determine the energy-volume and pressure-volume relationships for the different structures at T = 0 K. Murnaghan's EOS indicated that the transitions of cubic phase → tetragonal → rhombohedral → orthorhombic occur at 8.98, 16.40 and 16.90 GPa, respectively, indicating the possibility of obtaining other phases for BSO. In the second step, the stoichiometric and nonstoichiometric surfaces (0 0 1), (0 1 1) and (1 1 1) of BSO were studied as regard the surface energy and stability. The most stable non-stoichiometric surface is the SnO-terminated (0 0 1), while stoichiometric (0 0 1) and (0 1 1) surfaces may exist simultaneously. This condition had a direct implication in the crystal morphology that was analyzed by the Wullf Construction and allowed the construction of a morphological map for this material. Finally, the stoichiometric surface (0 0 1) with the BaO termination was selected for applications as a water catalyst, taking into account the ...