# Chris Marianetti, Ph.D.

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Assistant Professor of Materials Science & Engineering

Department of Applied Physics & Applied Mathematics at Columbia University

### Presentation

*Unlocking the Mysteries of Plutonium via High Performance Computing*

Plutonium is an element which is both central to our national security and a forefront of condensed matter physics. Elemental Pu displays exotic physical behavior that continues to defy explanation despite many years of intense research. However, recent theoretical developments in conjunction with massively parallelized computers are steadily untangling the mysteries of Pu. In this work, a combination of Density Functional Theory and the Dynamical Mean Field theory (DMFT) is used to calculate various electronic properties of Pu, such as the magnetic susceptibility, heat capacity, and the temperature dependence of the valence band photoemission spectra. The continuous-time hybridization expansion quantum Monte-Carlo is utilized to provide the first approximation-free DMFT solution of delta-Pu which includes the full rotationally-invariant exchange interaction. We predict that delta-Pu has a Pauli-like magnetic susceptibility near ambient temperature, as in experiment, indicating that electronic coherence causes the absence of local moments. Additionally, we show that volume expansion causes a crossover from incoherent to coherent electronic behavior at increasingly lower temperatures. Future calculations and their implications will be discussed.

### Biography

Chris Marianetti is an Assistant Professor of Materials Science and Engineering in the Department of Applied Physics and Applied Mathematics at Columbia University. Marianetti has a diverse academic background spanning numerous disciplines. He did his B.S. in the field of Welding Engineering at The Ohio State University. During this time, he also spent one year at the General Motors Technical Center working on robotic resistance welding. Marianetti continued along this path, earning a M.S. in Welding Engineering at The Ohio State University. His thesis research dealt with weld-metal hydrogen assisted cracking, a chronic problem in many high-strength steel weldments. He then moved in a different direction, earning a PhD in computational Materials Science and Engineering at the Massachusetts Institute of Technology. His thesis research focused on applying first-principles methods, such as Density Functional Theory (DFT) and Dynamical Mean-Field Theory (DMFT), to energy storage materials. Marianetti continued on to a post-doctoral position in condensed matter physics at Rutgers University where he continued developing/applying DFT and DMFT to strongly correlated electron systems. Following Rutgers, Marianetti moved on to a second post-doctoral position at Lawrence Livermore National Laboratory (LLNL) where he utilized LLNL's world-class supercomputers to apply DFT and DMFT to Plutonium. Marianetti then moved to the Department of Applied Physics and Applied Mathematics at Columbia University, where he is currently an Assistant Professor of Materials Science and Engineering. His research focuses on techniques to solve the many-body problem of solids from first-principles, and applying these techniques to technologically relevant materials including transition-metal oxides, actinides, and other materials with strong electronic correlations.