Aravind R. Asthagiri, Chemical Engineering, University of Florida, 427 ChE Bldg, PO Box 116005, Gainesville, FL 32611
The origin of the high piezoelectric response observed in complex solid solution perovskites like PbZn1/3Nb2/3O3-PbTiO3 (PZN-PT) or PbMg1/3Nb2/3O3-PbTiO3 (PMN-PT) is still not well understood. PMN is a relaxor with fascinating and controversial behavior, and is also the relaxor end member of the new high strain piezoelectric PMN-PT. Atomistic simulations will be important in gaining insight into these important materials. It is not practical to model these chemically disordered systems with first-principles and therefore an accurate potential model that is transferable across composition is required. We have developed a shell potential model for PMN-PT by fitting to extensive first-principles data of the end members. We will report on molecular dynamics (MD) results of the polarization behavior of PMN-xPT as a function of chemical ordering, temperature, applied electric field, and PT concentration. Our MD results reproduce the complex compositional phase diagram of PMN-xPT including the existence of a monoclinic phase in a small composition range. We will discuss preliminary work on examining pyrochlores using a similar approach. Our ongoing efforts to improve the accuracy of potential models for ceramics by the incorporation of charge transfer will be discussed.