**4. Investigation of piezoelectricity in perovskites using standard basis sets in barium titanate (BaTiO3) and lanthanum titanate (LaTiO3)**

In this section, we investigate the piezoelectricity in BaTiO3 and LaTiO3 perovskites. Initially, we apply the methodology for the BaTiO3 to verify if the results show the piezoelectricity property, once it is known this perovskite has it. After, we apply the same methodology for LaTiO3 and the results are analyzed to check the property. **Figure 2** shows crystallographic units of studied perovskites.
