Professor Lisa Fredin of Lehigh University

"Computational Materials Chemistry: Predicting Excited State Evolutions and Reactivity of Complex Systems"

Focusing on the development of models at the interface of experiment and theory, we use quantum chemistry to interrogate the chemical physics of disordered materials and improve fundamental understanding of structure-function relationships in complex electronic materials. We build models of complex materials, which are a mixture of local chemical effects and extended material electronic structures, for example packed organics, 2D organometallics, surfaces, and nanostructured interfaces. These computations are at the edge of our current computing power and address important problems in solar energy, molecular switching and sensing, as well as pushing computational science. Capitalizing on our expertise building experimentally accurate structural models and accurately applying quantum mechanics to large complex systems, we combine a multilevel modeling approach to provide new chemical understanding of real experimental materials including disorder, predicting interfacial chemistry, and untangling the photophysics and photochemistry of light harvesting molecules and nanomaterials. My group has designed new computational methods to predict experimentally relevant and measurable phenomena, as well as used fundamental theoretical studies to suggest new avenues for experimental study.

Specifically in this presentation I will show the progress we have made in our three main areas of study:

Disorder in Materials. My group has built methods for fully exploring computational parameter space in disordered inorganic materials including dopants, amorphous bulk, interfaces, and nanoparticles, as well as characterizing these important materials with high level quantum mechanics for the first time. These models will enable us to solve some of the hardest problems for quantum mechanics about surface chemistry. In addition, we have built models that include how inherent vibration in molecular materials effects their transport and increased the efficiency to predicting predict transport of whole molecular materials rather than dimers from the structure, we are now being able to predict how even zero-point vibrational energy in organic materials decreases the transport in them as well as being able to predict what chemical modifications might reduce these negative effects.

Photochemistry. We are developing new computational methods which combine our expertise predicting the photochemical properties of molecular switches, sensitizers, and photochemical reaction intermediates accurately and efficiently. These smaller systems provide important benchmarking information for the material models we build. In addition, through the Photochemistry Undergraduate Research Experience (PURE), an immersive research experience for early career undergraduates that combines experiment and computational training for students who only have a general chemistry level understanding of quantum mechanics, we have been able to expand these projects beyond potential energy curves to multidimensional potential energy surfaces and combine our materials expertise to pioneer a new initiative to model photoswitching in the solid state.

Interfacial Chemistry. Since structure at interfaces is often smaller than current spectroscopic limits, computational understanding of the geometric and electronic structure can provide insights into how to design more efficient charge or energy transfer or catalysis at interfaces. Applying our modeling methods, we recently were able to contribute to the understanding of the catalytic nature of even well studied TiO2. In our recently funded NSF CMSD-A project we will use the structural models we have built, to directly explore how corners and edges of particles affect their reactivity.