Event Time: Thursday, October 1, 2020 | 2:00 pm - 3:00 pm
Event Location:
Meeting ID: 657 8412 2083
Passcode: 113399
Add to Calendar 2020-10-01T14:00:00 2020-10-01T15:00:00 CM Seminar - The minimal physical picture needed to understand gapping, displacements, mass enhancement, and disproportionation in 3d Event Information: Abstract: In his seminal work, N. Mott theorized that the insulating behavior of 3d transition metal oxides emerges This perspective created a general position in the literature that mean-field  approaches such as DFT are inappropriate for describing the broad science issues of 3d oxides. The indispensability of the highly correlated approach builds upon illustrations  that DFT fails to explain the insulating  state of paramagnets, orbital ordering, mass -enhancement, even Jahn-Teller distortions. Upon a closer examination described here one finds  that these failures apply to  highly-symmetric minimal unit cell models containing only the least number of possible magnetic, orbital and structural degrees of freedom. We explored the alternative option of staying within mean field DFT, but avoiding Naïve (N)-DFT approximations that do not define what DFT can do. Specifically, we allow  symmetry breaking (such as  local displacements; avoiding equal occupation of  degenerate levels, avoid forcing zero moments on each atomic site in paramagnets) if it lowers the total DFT energy. This generalization creates (even without U)  finite band gaps in AFM and PM phases of ABO3 perovskites (except PM SrVO3 and CaVO3 that are metals), disproportionation (in SmNiO3 and YNiO3), mass enhancement (in SrVO3 ,LaMnO3 SrBiO3) and explains the observed trends in Jahn-Teller distortions throughout the series. Symmetry breaking in approximate mean-field theory could capture events that in restricted symmetric structures would require a complex correlated treatment. This  is consequential, as it opens the door for (non-naïve) DFT treatment of complex d electron systems  including interfaces, defects and doping that do not depend on details of multiplets.   Biography: Prof. Alex Zunger of the University of Colorado, Boulder research field is Condensed Matter Theory of Real Materials, involving foundational work on Density Functional Theory, Pseudopotential theory, Quantum Nanostructures, Photovoltaic materials and Materials by Design  ( website:; http://www.colorado.edu/zunger-matter-by-design/). He is widely credited with foundational work and leadership in the now classical field of “First Principles theory of solids”, a predictive approach to electronic, structural and thermodynamic properties of matter, given the atomic identities and composition. He published over 700 journal articles in this discipline, delivered many hundreds of talks in physics and materials societies,  and mentored 84 postdoctoral fellows, many of who are now leading scientists around the world.    He is the recipient of the year 2018 Boer Medal for photovoltaic research, the 2013 TMS Hume- Rothery Award on Theory of alloys, the 2011 (inaugural)  “Materials Theory Award” of the Materials Research Society on Inverse Design, the 2010 “Tomassoni Prize“ (Italy) and “2010 Medal of the Schola Physica Romana “ celebrating the tradition of E. Fermi, the 2001 John Bardeen award of The Material Society on “Spontaneous Ordering in semiconductor alloys”, the 2001 Rahman Award of the American Physical Society on ‘foundational development of First Principles methods’, and the 2009 Gutenberg Award (Germany) on correlated electron systems.  He is a Fellow of the American Physical Society; Fellow of the Materials Research Society, Sakler Fellow of the Institute of advanced studies (Tel Aviv University).  The impact of Dr. Zunger’s work is partially reflected by the high number of citations his papers have received (over 100,000, according to Google Scholar) and by his “h-number” of more than 145 (i.e., 145 of his papers were cited each at least 145 times).  He is the author of the fifth-most-cited paper in the 110-year history of Physical Review (out of over 350,000 articles published in that journal) .In the course of his research; he has authored more than 700 articles in refereed journals, which includes over 150 articles in Physical Review Letters and Rapid Communications (PRB) and three citation classics. Declared by the Institute of Scientific Information (ISI) as the 39th most-cited physicist out of more than 500,000 physicists examined, based on publications in 1981–1997 in all branches of physics.   Event Location: https://ubc.zoom.us/j/65784122083?pwd=U09vVXJMRzNLaTY3bmVXNEFJZ1k3UT09 Meeting ID: 657 8412 2083 Passcode: 113399