AbstractsPhysics

The perovskites ABO₃ are the most important class of dielectric materials. The perovskite SrTiO₃ and the perovskite-related material CaCu₃Ti₄O₁₂ are studied in this work. In the first part of this work, we find the structural temperature of SrTiO₃ by performing molecular dynamics simulations and investigate electronic and structural properties of SrTiO₃ by performing ab initio calculations. A strong chemical bonding nature between Ti and O is found. This is responsible for the TiO₆ octahedron behavior throughout the phase transition. In the second part, ab initio calculations on CaCu₃Ti₄O₁₂ are performed. We investigate the electronic properties of this material. An antiferromagnetic character of CaCu₃Ti₄O₁₂ is observed. Furthermore, we investigate the electronic properties of new materials of different Ca, Cu ratios. This is the first time to perform ab initio calculations to study Ca_1+xCu_3-xTi₄O₁₂. We find that with the increase of with increase of Ca in the material, the optimized lattice constant and band gap increase, and insulator character becomes much more pronounced in the material. This is in good agreement with the experimental results.