Study on optical and dielectric properties of CaCu3Ti4O12 by first-principles calculation

The electronic and optical properties of the high-dielectric-constant material CaCu3Ti4O12 (CCTO) are studied using density-functional theory within the generalized gradient approximation. The calculated electronic structure shows that CCTO is of a charge-transfer character. The optical functions are calculated and the optical spectra are given where all the peaks are assigned with a remarkable absorption peak around 3.5 eV, which is attributed to the charge-transfer transitions from O 2p to Cu 3d states. A discussion is made for the optical infrared anomalies in CCTO.