Harris Chemistry Group
Louisiana Tech University
Research in the group is centered around solids NMR spectroscopy and computational chemistry or whatever other techniques provide insight into various topics in materials chemistry, including rechargeable batteries.
Theory of NMR spectroscopy
Analytical and numerical Methods
NMR spectroscopy often involves assembling a large set of known elements into a larger experiment. While quantum mechanical in nature, a lot of these experiments are possible to understand in a back-of-the-envelope way, so it can be a fun problem solving exercise. More complicated experiments, such as that above, require computer simulations to determine how successfully the cartoon physics translates into real world success. We are interested in developing better fundamental understanding of these building blocks, and in in developing novel experimental methods.
Materials studies and electrochemical performance
There are many, many avenues of research with the potential to greatly improve rechargeable batteries. We are interested in tracking the chemical changes in the disordered and horrendously complicated active materials (anodes, cathodes, ion transporters), often via solids NMR spectroscopy. Changes in the local chemistry are then used to understand the electrochemical performance curves of the battery (above).
Atomically Thin Materials
Such as graphenes, MXenes, nanotubes, etc.
This new and important class of materials are too thin to form the stacks of regular atoms needed for diffraction-based structure studies. Furthermore, the sheet edges (and sometimes surfaces) are generally terminated with some kind of disordered chemical moieties. Solids NMR spectroscopy is really the only way to extract detailed information from such materials, and we are interested in developing NMR methods for these problems.
Relating Observed Properties to Bonding
Analyzing properties by using MOs
Most of us like chemistry because we can relate the behavior of materials to our understanding of the bonding. We are generally interested in relating the MOs to properties such as structure, reactivity, photochemistry, etc., and have a particular interest in relating the NMR observables such as chemical shifts, J-couplings, and quadrupole couplings to specific features of the MOs.
Structure of Disordered Solids
Tying proposed empirical models to experimental data
Many technologically interesting materials are produced using melt-quench methods. Some, like the rechargeable battery cathode shown above, display atomic positions that are regular and well defined but are occupied by a mixture of ions in a glassy distribution. For the extremely disordered varieties, experimental measurements cannot resolve specific sites out of the multitudes. We are interested in attempting to solve these intractable "structures" by assigning model energies to local interactions from chemical intuition or from computational data, and then predicting or refining structures versus experimental data.