We hybridize the swap Monte Carlo and geometric relaxation methods to determine the intrinsic compositional structure (CS) of the lead magnesium niobate (PMN) relaxor. We verify the stability of a Nb-rich sublattice in PMN, as prescribed by the prevailing random-site model. However, ions in the complementary sublattice are not randomly mixed. Most Nb ions collapse into a single percolating cluster with a mesh-like structure. This specific geometry serves to prevent large space charges, and this behavior differs from typical phase separation in metallic alloys. Subsequent molecular dynamics simulations predict a pair distribution function that is consistent with neutron scattering experiments. Analysis of dipolar structures in the Nb cluster sheds light on the unique dielectric properties of PMN.
Categories: cond-mat.mtrl-sci cond-mat.dis-nn cond-mat.mes-hall cond-mat.stat-mech