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My research focuses on atomistic computation of defects, defect interactions, and the mechanical behavior of materials. The main emphasis is to understand the effect of chemistry on mechanical properties; for example, directionality of bonding, or changes in chemical environment from solutes. I do this using computer simulations combined with mathematical models to make predictions of real material behavior. The goal of this research is both to understand the underlying atomistic phenomena at work in larger-scale material behavior, and to extend our ability to predict new behavior in novel materials.

The primary computational tools I use are electronic structure methods that accurately treat chemical bonding for interatomic forces. Often, the results of these computations feed into models for larger length-and time-scale behavior to predict material properties. I also work with and build approximate atomistic models that are computationally faster than electronic structure, to directly study longer length and time scales. Finally, I use and construct new techniques that extend the geometric limitations in electronic structure methods. Most recently, I used these new techniques to accurately compute dislocation-solute interactions for predictions of solid-solution softening.

Past highlights of my research come from structural metals and new alloys, such as

• The prediction of the atomistic-scale mechanism for a pressure-induced structural phase transformation in pure Ti. Finding the mechanism requires a new method for searching for crystal transformation pathways.
• The calculation of solute and interstitial effects on the alpha to omega transformation in Ti. This explained the role of as little as 1% oxygen in stopping the transformation in shock-loaded Ti.
• The first direct calculation of solute-dislocation interaction in Mo, to explain the 50-year old question of cause of solid-solution softening.