Oxide surfaces are increasingly important for both scientific and technological areas ranging from more energy-efficient catalysts to new types of electronic devices. Currently not enough is understood about the structure of oxide surfaces to predict what type of materials will be best for future needs. This project is developing tools to understand both the structure of oxide surfaces, as well as how they react with gaseous species. The tools that are developed can then be used by others who are designing interfaces involving these systems, or are exploring their use in new fuel cells, more efficient water-splitting catalysts or substrates upon which to grow new types of oxide-based electronic devices.
TECHNICAL DETAILS: The strategy employed combines extended density-functional theory (DFT) methods including exact-exchange hybrids and the bond-valence chemical concepts in a combined experimental-theoretical approach exploiting some unique ultra-high vacuum (UHV) electron microscopy facilities. The main experimental tools are transmission electron microscopy imaging and diffraction to solve the surface structures. In addition to using DFT methods for the surface structures found, the research team is expanding the database of published atomic positions and tests of the bond-valence approach by performing calculations on other oxide surfaces where full details of the atomic positions are not publically available. One additional component is developing algorithms for DFT and related optimization codes, particularly quasi-Newton methods. The software for DFT has already been incorporated into one large package used by more than 1800 groups around the world (www.numis.northwestern.edu). In terms of education, the research helps support both local outreach to high-school students as part of existing programs, as well as more international efforts involving the general public license (GNU) software electron direct methods (edm).
