Barium strontium titanate-based perovskite materials from DFT perspective: assessing the structural, electronic, vibrational, dielectric and energetic properties

This paper presents a current theoretical study on structural, electronic, vibrational, dielectric and energetic properties of the pristine cubic and tetragonal barium strontium titanate (BSTc and BSTt), as well as Sn-doped cubic and tetragonal barium strontium titanate (BSTSc and BSTSt) crystals. For this purpose, first-principle calculations within the Density Functional Theory method at the B3LYP level are implemented in the CRYSTAL14 code. Structural and thermodynamic analysis indicates that the change in geometry, as well as the Sn-doping process in BST samples, induces structural defects, which govern its electronic structure, generating singular bandgap values attributed to the perturbation of electronic levels in the vicinity of the Fermi level. Moreover, the vibration analysis was helpful to identify how the Sr and Sn doping process along with the A- and B-site of perovskite structure can affect the structural disorder, mainly for the tetragonal phase. Besides, electron density maps showed that the electronic properties were associated with the presence of [AO12] (A=Ba and Sr) and [MO6] (M=Ti and Sn) clusters with distinct bonding character. Furthermore, our structural, vibrational, and electronic calculations are in good agreement with the available experimental data and pave the avenue towards the complete understanding of the overall properties of perovskite materials.