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SUMMARY:Excited states\, symmetry breaking\, and multiple solutions in ele
 ctronic structure theory - Dr Hugh Burton\, Oxford
DTSTART:20230313T143000Z
DTEND:20230313T150000Z
UID:TALK197803@talks.cam.ac.uk
CONTACT:Dr Christoph Schran
DESCRIPTION:Excited states are essential for understanding photochemical p
 rocesses\, ranging from photosynthesis and biological mechanisms of vision
 \, to photocatalytic reactions and optoelectronics. However\, accurate sim
 ulations of high-energy\, charge transfer\, or double excitations remain d
 ifficult with state-of-the-art techniques based on linear response theory.
  This talk will focus on an alternative "state-specific" perspective where
  excited states are represented by higher-energy variational stationary po
 ints of the electronic energy landscape. Firstly\, I will describe the str
 ucture of the exact electronic energy landscape\, the topological properti
 es of exact excited states\, and how approximate wave function ansätze fo
 rm constrained subspaces. I will then characterise the different solutions
  that can be identified using a single Slater determinant or multiconfigur
 ational wave function approximations in typical molecular systems. These e
 xamples highlight that state-specific excitations can provide compact repr
 esentations of high-energy\, charge transfer\, and double excitations\, wh
 ile also demonstrating the challenges that must be addressed to achieve pr
 actical calculations in the future.
LOCATION:Department of Chemistry\, Cambridge\,  Pfizer Lecture Theatre
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