Ab initio study on ferroelectric oxide AT1O3 (A=Sr, Ba, Sn, Pb) by using Density Functional Theory / Khairul Helmy Kamalul Arifin

The first principle study using Density Functional Theory (DFT) and Local-density Approximation (LDA) is studied to calculate electronic band structure and density of states (DOS) of ferroelectric oxide AT1O3 (Sr, Ba, Sn, Pb). The calculations include its bulk, BaTi03, SrTi03, PbTi03 and SnTi03, and superlattices BaTi03/SrTi03) PbTi03/SrTi03 and SnTi03/SrTi03 with SrTi03 is treated as substrate of the superlattices. For bulk ferroelectric compounds, the calculated energy gap in the band structure of SrTi03, BaTi03, PbTi03 and SnTi03 is 1.864 eV, 1.776 eV, 1.549 eV and 0.967 eV respectively. The interaction exists in the density of states of each compounds is studied as to determine the ferroelectric behaviour in each compounds. The calculated energy gap of BaTi03/SrTi03, SnTi03/SrTi03 and PbTi03/SrTi03 superlattices is 1.895 eV, 1.467 eV and 1.958 eV respectively. Hence the difference between each superlattice compounds and bulk BaTi03, PbTi03 and SnTi03, is studied and show in good agreement. Lastly, phonon dispersion curves and lattice dynamic of bulk BaTi03, SrTi03, PbTi03 and SnTi03 is evaluated and found that these compounds having possibilities to transform into the lowest symmetry phase which are tetragonal, orthorhombic and rhombohedral below its Curie temperature (Tc).