Antiferrodistortive phase transition in Pb(Ti0.48Zr0.52)O3:: Space group of the lowest temperature monoclinic phase -: art. no. 212101

Ranjan [Phys. Rev. B 65, 060102(R) (2002)] have recently presented results of a powder neutron-diffraction study of the high-temperature monoclinic (F-M(HT)) to low-temperature monoclinic (F-M(LT)) phase transition in Pb(Ti1-xZrx)O-3 discovered by Ragini [Phys. Rev. B 64, 054101 (2001)]. They attribute the presence of superlattice reflections in the diffraction data to tilting of oxygen octahedra and propose a monoclinic space group Pc for the F-M(LT) phase. It is shown that for the model proposed by Ranjan , the correct space group of the F-M(LT) phase should be Cc. This has also been corroborated by a group-theoretical approach to the problem. A different set of refined structural parameters for the Cc space group obtained from the Rietveld analysis of the powder neutron-diffraction data of Ranjan is also presented.