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Speaker: Alex Hampel, CCQ
Title: Downfolding & calculation of screened Coulomb interaction in DFT
Abstract:DFT+ methods like DFT+U or DFT+DMFT are commonly utilized to improve the description of DFT for strongly correlated electron systems. An important step in this procedure is to identify a suitable set of localized orbitals in which DFT lacks a proper description of strong electronic correlation effects. These orbitals define a correlated subspace in which more sophisticated methods treat the additional Coulomb interaction. The transformation from the Kohn-Sham states to this correlated subspace is denoted as downfolding, projecting out all other states already accounted for properly in DFT. However, the effective Coulomb interaction in this correlated subspace is no longer atomic like, but rather screened by all other electrons outside the correlated subspace. In this talk, I will give a brief overview over two prominent methods to calculate the effect of screening and to extract appropriate effective Coulomb interaction tensors in DFT+ methods: the constrained random phase approximation (cRPA) and constrained LDA (cLDA).