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Cyrus Dreyer: Quantum Embedding for Point Defects: Case Studies and Challenges

Date and Time
Location
Elings Hall 1601
Cyrus Dreyer

Abstract:

Point defects, including vacancies, interstitials, antisites, and impurity atoms, are ubiquitous in all materials and can have a profound influence on their properties. Density-functional theory (DFT) calculations have proven to be a crucial tool for defect identification and characterization. However, such calculations have fundamental limitations, e.g., for excited electronic states that may have correlated, multireference nature. This motivates the application of many-body methods to treat such cases. However, the large system sizes necessary to treat isolated defects in their bulk host constitutes a challenge for many-body methods because of their computational cost. Recently, quantum embedding approaches, where a small set of states is treated via many-body methods as a correlated active space, while the weakly-correlated bulk is treated with DFT, have shown promise for defects. In this talk, I will describe one such approach, based on Wannierization of defect orbitals and constrained random-phase approximation calculation of screened Coulomb interactions. I will demonstrate this technique with several test-case defects including carbon-based defects in BN, the nitrogen-vacancy center in diamond, and Fe in III-nitride semiconductors, illustrating its promise and potential challenges.

Bio:

Cyrus Dreyer earned a B.S. in Engineering Science and Physics, and a B.A. in Mathematics from the University of Virginia. He earned a Ph.D. in Materials from the University of California, Santa Barbara, and then was a postdoctoral associate at Rutgers University. He is now an affiliate associate research scientist at the Flatiron Institute Center for Computational Quantum Physics, and an assistant professor at Stony Brook University in the department of Physics and Astronomy. His research interests involve developing and implementing computational techniques based on density functional theory to explore the properties of electronic materials.