Lattice dielectric response of CdCu3Ti4O12 and CaCu3Ti4O12 from first principles -: art. no. 012103

Structural, vibrational, and lattice dielectric properties of CdCu3Ti4O12 are studied using the density-functional theory within the local spin-density approximation, and the results are compared with those computed previously for CaCu3Ti4O12. Replacing Ca with Cd is found to leave many calculated quantities largely unaltered, although significant differences do emerge in zone-center optical phonon frequencies and mode effective charges. The computed phonon frequencies of CdCu3Ti4O12 are found to be in excellent agreement with experiment, and the computed lattice contribution to the intrinsic static dielectric constant (similar to60) also agrees exceptionally well with a recent optical absorption experiment. These results provide further support for a picture in which the lattice dielectric response is essentially conventional, suggesting an extrinsic origin for the anomalous low-frequency dielectric response recently observed in both materials.