REEXAMINATION OF THE ANTIFERROELECTRIC STRUCTURE OF PBZRO3

The crystal structure of antiferroelectric PbZrO3 was re-examined by h igh resolution powder neutron diffraction. The structure obtained with assumed modulations associated with the lattice vibrational modes Sig ma(3)(TO) and R-25(xy) is almost the same as that obtained previously with the same assumptions. However, one coordinate of oxygen positions obtained by the refinement for all crystallographically possible para meters is different from that obtained previously under the same condi tions. The difference between the two sets of the structural parameter s obtained here is meaningful. The result indicates that the modulatio n associated with the R-25(xy) mode is fairly distorted. This structur e agrees well with that recently investigated using local-density calc ulations.