  Crystalline structures, zone-center phonon modes, and the related dielectric
response of the three low-pressure phases of HfO2 have been investigated in
density-functional theory using ultrasoft pseudopotentials and a plane-wave
basis. The structures of low-pressure HfO2 polymorphs are carefully studied
with both the local-density approximation (LDA) and the generalized gradient
approximation (GGA). The fully relaxed structures obtained with either
exchange-correlation scheme agree reasonably well with experiment, although LDA
yields better overall agreement. After calculating the Born effective charge
tensors and the force-constant matrices by finite-difference methods, the
lattice dielectric susceptibility tensors for the three HfO2 phases are
computed by decomposing the tensors into the contributions from individual
infrared-active phonon modes.
