Not All Projectors Are Equal: Frontier Wannier Functions for DFT+U and Linear-Response U

by Maria Andolfatto (PSI)

Wednesday 30 Sept 2026, 15:00 → 16:00 Europe/Zurich

OVGA/200

DFT+U is one of the most widely used methods for correcting the self-interaction error of approximate density functionals in systems with localized d or f electrons. However, its predictions depend strongly on the choice of the Hubbard projectors that define the localized manifold. Standard implementations rely on atomic-like projectors, which are fixed, system-independent, and not necessarily representative of the states that actually drive the physics of the material.

In this talk, I will discuss an alternative approach based on frontier Wannier functions, which are constructed from the states near the Fermi level and therefore adapt to the chemical environment of the system. I will compare them with conventional Hubbard projectors, analyzing the differences in the Hubbard U computed from first principles via linear-response theory and in the resulting ground state, both through a formal derivation and through numerical simulations. This comparison shows that the choice of projector is not a technical detail but a central ingredient of a predictive DFT+U description.