Oxide Surfaces, From Bulk to Nanoparticles

Northwestern University, Evanston IL

Investigators

Abstract

NON-TECHNICAL DESCRIPTION: Oxide surfaces are an important frontier, with applications in many areas of technological importance ranging from catalysis to the emerging field of oxide electronics. Our understanding of oxide surfaces is relatively primitive and for future commercial applications industry will demand five-sigma controlled growth of oxides both at the large scale and at the nanoscale, which will require quantitative understanding of how the surface structures depends upon the conditions used to make the materials. This work targets determining the key concepts to enable design of oxide surfaces for specific applications in catalysis as well as to control the growth of oxide thin films and for other applications. In addition to activities in supporting minority and underrepresented students within Prof. Mark's group, this project also supports work assisting users from more than 2000 groups around the world using the Wien2k software from 84 different countries which range from developed countries such as the USA, Spain, and Sweden to developing countries such as India and under-developed countries such as South Sudan and Egypt. TECHNICAL DETAILS: The project poses the questions of what is the atomic structure of the surface of more complex oxides at both the mesoscale and in nanoparticles, how does this connect to the kinetics of growth or thermodynamics, and what are the predictive rules for oxide surface structures at both size scales? If we do not know the positions of the atoms at the surface, it is impossible to explain phenomena such as different shapes of nanoparticles on different reconstructions and how this changes their catalytic behavior; different growth modes of technologically important materials on different reconstructions; different chemical reactivity on different surface reconstructions as well as the unspoken irreproducibility of oxide growth experiments. To unravel this information the project is a combined experimental-theoretical effort combining oxide surface science methods with higher resolution transmission electron microscopy, density functional theory methods and continuum based modelling. In addition to the underlying science of oxide surfaces, the project involves training of graduate and undergraduate students in cutting-edge research methods, assistance to scientists around the world as users of the Wien2k density functional code and general science outreach via the development of Wikepedia pages by graduate students.