First-principles calculations of phonon dispersion and lattice dynamics in La2CuO4

First-principles density-functional linearized augmented plane-wave linear-response calculations are presented of the lattice dynamics of tetragonal La2CuO4. Phonon frequencies and eigenvectors are obtained throughout the Brillouin zone. Generally good agreement is achieved with experiment, but frequencies of the lowest-lying branches, which involve anharmonic motion of the epical oxygen atoms parallel to the CuO2 planes, are underestimated. The octahedral tilt mode at the X point is found to be the most unstable mode throughout the Brillouin zone, consistent with the observed phase transition to the orthorhombic structure at low temperature. The calculated dispersion of the highest frequency Sigma(3) branch is in good agreement with experiment, showing that a proposed large renormalization of the phonon spectrum by a Jahn-Teller electron-phonon interaction is unlikely. [S0163-1829(99)12513-X].