Thomas Underwood

Clays in the Computer

When most people hear the word "geology", the images that come to mind might include the following: Towering snow-capped mountains, vermillion rust-infused cliffs, massive mazes of mines filled with shimmering gold and brilliant gemstones. But what if we were to go smaller? Much smaller. One billionth of a meter, perhaps? What would we see?

Dr. Thomas Underwood, a colleague of the department's Professor Bickmore, presented his work at the March 20, 2025 seminar analyzing the characteristics of clay at a molecular level and its implications. Dr. Underwood is a postdoctoral research associate and a computational chemist at the Pacific Northwest National Laboratory (PNNL), a government research facility dedicated to furthering progress in various fields, including earth sciences. He specializes in studying geochemical processes using molecular simulations. Prior to working at PNNL, he worked as a postdoctoral research associate at Princeton University. He received his Ph.D. from Durham University and a master's degree from the University of York.

Dr. Underwood began the presentation by posing a question: "How important are tiny interactions?" As a scientist who studies molecular processes and reactions, for Dr. Underwood, tiny interactions have been paramount, both within the scientific realm and in his personal life. Throughout his presentation, he would showcase many of the tiny interactions that he had with his mentors that led him to where he is today. One of these was with Dr. Martin Smalley, a professor at the University of York. Dr. Underwood approached Dr. Smalley to ask for help in coming up with an idea for his capstone project, to which the professor responded by handing him a beaker filled with an unknown cloudy substance. He asked Dr. Underwood to sprinkle a thimble of table salt into the beaker and watch what happened. Upon doing this, an amazing phase shift occurred; the cloudy substance, which turned out to be clay minerals, gathered at the bottom of the vial while the salt floated on the top. This occurrence would spark an intense interest in Dr. Underwood, leading to his capstone project, where he used equations to describe the phase property he had witnessed.

He continued the presentation by explaining in detail the molecular structure of clay minerals as well as some of the odd behaviors that clay molecules exhibit. A video was shown of a clay mineral called vermiculite absorbing a solvent and then rapidly expanding in only a vertical direction, as opposed to multiple directions. He explained the oddity by showing the clay particles under a nanoscale, where it was revealed that the particles have an incredibly large surface area to volume ratio. Clay particles are only one nanometer thick but can be hundreds of nanometers wide, which is why on a much larger scale the vermiculite reacted the way that it did.

He proceeded to further describe the properties of clay particles and their molecular structures, showing a series of simulations created by supercomputers. Computational algorithms are an enormous aspect of Dr. Underwood's work, and it's within these simulations that he can observe interactions between particles. He also uses several different advanced methods that assist him in his computations of atomic forces and system energy. These include x-ray diffraction, where the structure of the molecule is identified; electrostatics, which looks at electrical charges; dispersion interactions, which describe interactions between neutral atoms; and testing covalent bonds and angles.

After going into a much deeper dive into the science and processes of his work, Dr. Underwood gave some insight into what motivates him. His expertise in molecular-scale models helps him to understand large-scale societal issues. For example, the Utah FORGE laboratory is working to improve how we harness geothermal energy. Through Dr. Underwood's work, methods are being developed to have more consistent, secure, and cleaner sources of energy. This project and others lead to massive impacts on the qualities of our lives.

So, just how important are tiny interactions? Dr. Underwood concludes that, thanks to all of the many tiny interactions he's had over the years, his life has been impacted on a profound level. Tiny interactions shape the world around us. They lead to much larger interactions that have real-world implications that can improve our lives. He finished by inviting the students to reflect on how their tiny interactions with other people can help make a positive and notable impact.

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