Experimental and first-principles investigation of structural, electronic, optical, elastic and ferroelectric properties of BaTiO3

Structural, electronic, optical, elastic and ferroelectric properties of lead-free BaTiO3 perovskite has been investigated experimentally and theoretically by DFT + U calculations with U = 5 eV using Quantum ESPRESSO code. The ceramic sample was synthesized through solid-state reaction method and its detailed structural investigation done by combined Rietveld (JANA 2020), Pair Distribution Function (PDF) and Raman analysis. The calculated structural properties including the frequency position of Raman lines are found to be in good agreement with experimental results and the electronic study shows that the calculated band structure of tetragonal BaTiO3 at Γ point has an direct energy gap (Eg) about 3.43 eV. Optical parameters and also the elastic constants were computed and compared with the available experimental data. Spontaneous polarization of 0.34 C/m2 for tetragonal BaTiO3 was calculated using Berry phase calculation and it is comparable with the experimental value of 0.20 C/m2.