Finite-temperature properties of the relaxor PbMg1/3Nb2/3O3 from atomistic simulations

An atomistic numerical scheme is developed and used to study the prototype of relaxor ferroelectrics, that is PbMg1/3Nb2/3O3 (PMN), at finite temperatures. This scheme not only reproduces known complex macroscopic properties of PMN, but also provides a deep microscopic insight into this puzzling system. In particular, relaxor properties of PMN are found to originate from the competition between (1) random electric fields arising from the alloying of Mg and Nb ions belonging to different columns of the Periodic Table within the same sublattice; (2) the simultaneous condensation of several off-center k points as a result of a specific short-range, antiferroelectriclike interaction between lead-centered dipoles; and (3) ferroelectriclike interactions. Such origins contrast with those recently proposed for the homovalent Ba(Zr,Ti)O-3 solid solution, despite the fact that these two materials have similar macroscopic properties-which therefore leads to a comprehensive understanding of relaxor ferroelectrics.