Visualizing electronic structure changes across an antiferroelectric phasetransition: Pb2MgWO6

Pb2MgWO6 is an ordered perovskite or elpasolite that undergoes a phase tran sition from a cubic paraelectric phase to an orthorhombic antiferroelectric phase below 310 K. Through an analysis of the electronic structures of bot h the high and low temperature phases using high level band structure metho ds, the nature of the changes in the bonding across the phase transition ha s been examined. The key stereochemical role of the lone pairs on the lead atoms has been examined by use of the Electron Localization Function. While the lone pairs on the lead atoms are smeared out by the near octahedral sy mmetry of the lead sites in the high temperature phase, at low temperatures they localize into the traditional lobes. These changes have been visualiz ed.