Electronic Structure of Bulk and Defected CaCu3Ti4O12

The calcium copper titanate CaCu3Ti4O12 is a distortedperovskite exhibiting a giant dielectric constant withnon-ferroelectric temperature behavior. Recent investigationstend to attribute the origin of the anomalous behavior ofCaCu3Ti4O12 dielectric properties to the presence ofheterogeneous microstructure and grain boundary layers,excluding that the giant dielectric constant is present inperfectly stoichiometric, defect-free crystals. The intrinsicorigin is also ruled out by the normal dielectric behaviorobtained in ab initio Density Functional Theory (DFT)calculations. In this work, we present ab initio calculationsperformed to estimate the energies associated with the creationof defects in the CaCu3Ti4O12 lattice, including oxygen andcopper vacancies, and investigate their electronic properties.Furthermore, with a view at ascertaining whether correlationeffects may modify the electronic structure and dielectricity ofCaCu3Ti4O12, we present an application to CaCu3Ti4O12 of aDFT-based pseudo-selfinteraction-correction (pSIC) method already applied successfully to Mott insulators.