Abstract: One of the grand challenges in modern material science is the theoretical design of correlated materials with novel properties using first principles. Dynamical mean field theory (DMFT) has been a successful method for the study of the electronic structure in strongly correlated materials, especially when it is combined with density functional theory (DFT).
In this talk, I will present an open-source computational package developed for combining DMFT with various DFT codes. Features of this package include an interface with the wannier90 code, a library mode for an efficient linking of the package to an arbitrary DFT code, and a user-friendly Python interface with various post-processing tools. Results of electronic structures for well-known correlated bulk materials obtained using our DFT+DMFT package will be compared with those obtained from other DMFT codes and experimental spectroscopic measurements.
More importantly, this package has been applied to the study of oxygen vacancy or defect effects on the electronic structure of transition metal oxides. LaNiO3 exhibits a correlated metallic state in bulk. but it undergoes a metal-to-insulator-to-metal transition accompanied by magnetism as oxygen vacancies are increased. Using DFT+DMFT, we studied the change in the electronic structure of oxygen-vacancy ordered LaNiO3 and compared it with available experimental spectroscopic data when conventional DFT or DFT+U could not capture the spectroscopic features. We also clarified the nature of the insulating state in LaNiO2.5 as the site-selective Mott phase originating from both structural and charge-transfer effects, which is significantly different from the result of the homogeneous vacancy scenario. Moreover, I will also explain the strongly correlated nature of the metallic LaNiO2, which has been discussed intensively because of the recently discovered superconducting phase in this material.
Bio: Dr. Park received a B.S. from the Pohang University of Science and Technology in South Korea, and a Ph.D. from Rutgers University. He is an assistant professor in the physics department at the University of Illinois--Chicago with a joint appointment in the Materials Science Division at Argonne National Laboratory.