  We have performed a first-principles study of the structural and vibrational
properties of the three low-pressure (cubic, tetragonal, and especially
monoclinic) phases of ZrO2, with special attention to the computation of the
zone-center phonon modes and related dielectric properties. The calculations
have been carried out within the local-density approximation using ultrasoft
pseudopotentials and a plane-wave basis. The fully relaxed structural
parameters are found to be in excellent agreement with experimental data and
with previous theoretical work. The total-energy calculations correctly
reproduce the energetics of the ZrO2 phases, and the calculated zone-center
phonon frequencies yield good agreement with the infrared and Raman
experimental frequencies in the monoclinic phase. The Born effective charge
tensors are computed and, together with the mode eigenvectors, used to
decompose the lattice dielectric susceptibility tensor into contributions
arising from individual infrared-active phonon modes. This work has been
partially motivated by the potential for ZrO2 to replace SiO2 as the
gate-dielectric material in modern integrated-circuit technology.
