NSF Award
1505343
NON-TECHNICAL SUMMARY<br/><br/>This award supports theoretical and computational research and education on a suite of theoretical tools that will quantify electron delocalization on metal surfaces. Chemical reactions on metal and metal oxide surfaces are central to phenomena from heterogeneous catalysis to corrosion to the properties of metal nanostructures. Quantum mechanics postulates that the electrons in a molecule, solid, or surface are not spatially restricted to one point, but delocalize in a region of space. For example, the covalent bonds that hold molecules together involve electrons delocalizing between atoms. Chemical reactions converting iron into rust, or simple molecules into pharmaceuticals, must break bonds and temporarily re-localize electrons to atoms. Better understanding of delocalization in surface chemistry could have an enormous impact on developing industrial catalysts, nanomaterials, and many other systems.<br/><br/>Unfortunately, our understanding of delocalization on surfaces faces two major limitations. First, delocalization is a fundamentally non-classical and non-intuitive phenomenon. Second, the equations modeling the interaction of electrons with each other generally cannot be solved exactly. The standard approximations used in computer simulations of electrons on metal surfaces are particularly inaccurate for the delocalized and stretched bonds which are important in catalysis. More accurate approximations often require enormously demanding computational resources. Accordingly, better models would be a tremendous benefit. The PI has developed new tools that quantify electronic delocalization in space. This award supports application of these tools to the fundamental and practical problems associated with electron delocalization on metal surfaces. <br/><br/>This project integrates teaching and undergraduate research, providing specific research projects for undergraduate researchers and specific mentoring roles for graduate students. The PI will also develop an online component for his new course "Computational Chemistry for Experimentalists", aimed at providing non-specialist users at his institution and around the world with a practical introduction to electronic structure theory. <br/><br/>TECHNICAL SUMMARY<br/><br/>This award supports theoretical and computational research and education on a suite of theoretical tools that will quantify electron delocalization on metal surfaces. Chemical reactions on metal and metal oxide surfaces are central to phenomena from heterogeneous catalysis to corrosion to the properties of metal nanostructures. Computational models of reactions at surfaces must capture both the non-classical delocalization of electrons in chemical bonds, and the correlation-induced re-localization that occurs during bond breaking. The standard density functional theory approximations in surface science have major limitations for modeling these effects. This leads to significant errors in predicted reaction rates. <br/><br/>The PI's group has developed and implemented a suite of tools, based on the one-particle density matrix, which quantify delocalization in calculated wavefunctions. The team will use these tools to quantify how the presence of a catalyst surface affects the delicate interplay between delocalization and correlation-induced "re-localization" central to bond breaking and reaction rates. They will also use the tools in real-space models of non-dynamical correlation for computationally tractable treatments of chemistry at metal surfaces. The fundamental ingredient in such models is the extent to which an electron at a given point delocalizes past the expected length scale of a standard (generalized gradient approximation) density functional. <br/><br/>This project integrates teaching and undergraduate research, providing specific research projects for undergraduate researchers and specific mentoring roles for graduate students. The PI will also develop an online component for his new course "Computational Chemistry for Experimentalists", aimed at providing non-specialist users at his institution and around the world with a practical introduction to electronic structure theory.
