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SUMMARY:Koopmans spectral functionals: Bridging density-functional and man
 y-body perturbation theory
DTSTART:20250923T090000Z
DTEND:20250923T100000Z
DTSTAMP:20260816T100500Z
UID:indico-event-18043@indico.psi.ch
CONTACT:markus.mueller@psi.ch
DESCRIPTION:Speakers: Nicola Colonna (PSI / LMS)\n\nAccurate first-princip
 les predictions of spectral properties of materials are key to understandi
 ng\, discovering and designing materials for countless applications - from
  electronics to energy harvesting and photonics. Koopmans spectral functio
 nals provide a novel and functional approach - as opposed to diagrammatic 
 techniques - to simultaneously and accurately describe ground state prope
 rties and charged excitations - i.e.\, the electronic band structure - of 
 atoms\, molecules\, nanostructures and periodic crystals. This is achieved
  by augmenting standard density functionals with simple\, yet physically m
 otivated orbital-density-dependent corrections based on the three constrai
 nts of linearization\, localization\, and screening\, to enforce the corre
 ct description of charged excitations.\n \nAfter introducing the general 
 framework and its theoretical foundation\, I will discuss an extension of 
 the theory to fully and consistently incorporate the spin degree of freedo
 m. In this formulation\, state-dependent potentials emerge that can be int
 erpreted as a local counterpart to the electronic self-energy\, albeit alr
 eady accounting for spin-dependent interaction and screening effects beyon
 d the random phase approximation typical of standard diagrammatic approach
 es (GW). I will present theoretical evidence supporting this view and nume
 rical simulations demonstrating excellent agreement with experiments and s
 tate-of-the-art Green's function methods in predicting ionization potentia
 ls of a large set of molecules (the GW100 test set)\, as well as photoemis
 sion and absorption spectra of organic donors and acceptors\, and band gap
 s and band structures of semiconducting and insulating crystalline materia
 ls. Being this a functional framework\, the straightforward advantages are
  that forces and other derivatives are also readily accessible\, and that 
 the numerical parameters are those typical of density functional calculati
 ons. \n \n\nhttps://indico.psi.ch/event/18043/
LOCATION:WHGA/121
URL:https://indico.psi.ch/event/18043/
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