First-principles phonon calculations for La2CuO4.

Abstract

Full potential, linearized, augmented plane wave, total-energy calculations predict that the breathing mode in ${\mathrm{La}}_{2}$Cu${\mathrm{O}}_{4}$ is a high-frequency mode, in agreement with experiment and contrary to previously published results. We also find the experimentally observed tilt mode to be unstable within the local-density approximation. Eight other modes were studied, and excellent agreement with experiment was found, indicating that the local-density approximation gives accurate total energies and static density response for the high-temperature superconductors.