A MODEL OF LOCAL ATOMIC STRUCTURE IN THE RELAXOR FERROELECTRIC Pb(Mg1/3Nb2/3)O-3

We have developed a model of local atomic structure in the relaxor ferroelectric Pb(Mg1/3Nb2/3)O-3 (PMN) by pair-density function analysis of neutron and x-ray powder diffraction data. We find large static displacements of all atomic species from their ideal cubic perovskite sites producing a long-range average structure consistent with a crystallographic disorder model, however local correlations of these displacements are significant. Two distinctly different B cation environments are found, as are two unique environments for Pb. The model suggests the formation of structurally ordered regions in which the two types of B cation environments are 1:1 ordered. Details of this model for the local atomic structure of PMN and how it was obtained are described.