Finding Our Way by Following Electrons: Energy Chemistries Through Electronic Structure Theory

­As global energy consumption continues to rapidly expand, clean energy technologies become increasingly necessary. In this context, my research employs electronic structure simulations in two promising areas: chemical catalysis and solar energy. In addition to gaining fundamental descriptions of new chemistries, these studies have specific implications for the advancement of energy technologies, including hydrogen storage, carbon dioxide reduction, hydrocarbon conversion, and organic solar cells. Breakthroughs in these technologies could lead to zero emission vehicles, carbon neutral fuels, better utilization of fossil fuel feedstock, and inexpensive solar electricity.

In recent years, electronic structure simulations have become standard tools for providing molecular level information. The widespread use of simulations results from their ability to provide otherwise unattainable chemical mechanisms, as well as to supply guidance and interpretation to experiment. Although many simulation techniques have proven qualitatively useful, further development is needed to attain quantitative predictions. For instance, detailed investigation of quantum mechanical/molecular mechanical simulations of zeolites (Zimmerman et al., JCTC, in press) demonstrates that accurate simulations are achievable, but only with careful (and transferable) parameterization. Our new, fast and accurate model is actively being utilized to simulate catalysis in zeolites, including natural gas upgrading and alkane cracking. For solar research, simulations have typically relied on time-dependent density functional theory (TD-DFT) to investigate responses of molecules to light. This approach, however, is qualitatively incorrect for describing multiple exciton generation in organic materials. More sophisticated methods, such as restricted active space double spin flip configuration interaction (RAS-2SF), are required to gain fundamental insight into these processes. RAS-2SF breaks through limitations of TD-DFT and is able to explain the intermolecular mechanism that leads to efficient multiple exciton generation (Zimmerman et al., Nature Chem. 2010). The mechanisms elucidated in these studies are able to suggest design principles for exploiting the underlying chemical processes. Continued development and application of novel molecular simulation methods will be essential for the design of practical clean energy solutions.