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SUMMARY:A different perspective on charge disproportionation/order probed 
 by resonant X-ray scattering experiments: Insights from dynamical mean fie
 ld theory - G. Lucian Pascut\, Stefan Cel Mare University (USV)\, Suceava\
 , Romania
DTSTART:20231113T140000Z
DTEND:20231113T143000Z
UID:TALK208354@talks.cam.ac.uk
CONTACT:Dr Sun-Woo Kim
DESCRIPTION:Starting from the chemical principle of charge neutrality\, on
 e can make assumptions regarding the oxidation states of elements in compo
 unds based on transition metals\, particularly in the insulating states. H
 owever\, a more accurate method for estimating oxidation states is the bon
 d valence sum model\, which utilizes experimental crystal structures. Thes
 e estimates sometimes yield fractional oxidation states\, which are verifi
 ed by experimental techniques like resonant X-ray scattering (RXS) that em
 ploy empirical arguments. \nDespite its validity\, the interpretation of R
 XS experiments using numerical methods often indicates minimal charge disp
 roportionation\, which contradicts the estimated oxidation states. Additio
 nally\, RXS predicts charge disproportionation in metallic systems\, such 
 as the example of 2H-AgNiO2. In this presentation\, I will provide a conci
 se explanation of the fundamentals of the RXS method. Furthermore\, employ
 ing the dynamical mean field theory (DMFT)\, I will introduce an alternati
 ve perspective on chemically estimated oxidation states\, using compounds 
 like NdNiO3\, CaFeO3\, LaMnO3 and BiMnO3\, as examples. This new alternati
 ve perspective suggests that the presence of "charge disproportionation" i
 n materials is synonymous with the emergence of unique states of matter ch
 aracterized by site or orbital selectivity. In these novel states\, we obs
 erve intriguing phenomena such as non-equivalent crystallographic sites ex
 hibiting characteristics of both Mott and band-like insulators\, or within
  the same crystallographic site\, the coexistence of metallic and insulati
 ng orbitals.\n
LOCATION:Zoom link: https://zoom.us/j/92447982065?pwd=RkhaYkM5VTZPZ3pYSHpt
 UXlRSkppQT09
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