1. NU-MRSEC Northwestern University DMR-0076097SeedsLaurence Marks and Mark AstaSurface Phase Diagrams & Charge Redistribution in Oxides Knowledge of the atomic structure and charge redistribution at oxide surfaces is central to understanding of a wide variety of properties relevant to catalysis and thin-film technologies. We have developed a framework for the solution of multicomponent oxide surface structures employing a unique combination of first-principles calculations and direct-methods analysis of diffraction data. The approach has been extended to the study of the complex high-temperature c6x2 reconstruction for SrTiO3 (100). A hierarchical computational framework has been developed to perform automated searches for global-minimum-energy structures, leading to the identification of the candidate reconstructions shown below. Simulated STM images establish that the bright contrast observed in experiments are associated with surface Ti atoms, and lead to a model for observed surface defects based on the presence of TiO2 “ad-molecules”. Direct methods analysis based on the computed structures leads to a surface-structure model consisting of disordered arrangements of the structural sub-units displayed below.