Due to its computational efficiency and general good accuracy, density-functional theory (DFT) and time-dependent DFT (TDDFT) are currently the methods of choice for describing ground and excited state energetics of large molecular systems. These widely used techniques are applied to many problems in biological, chemical, and materials sciences. Despite not having the exact exchange-correlation (xc) potential V<sub>xc </sub>that maps the set of many-body interacting electrons to a set of non-interacting electrons with the same electron density as the interacting system, the approximate xc potentials thus far developed have performed well in practice for both the ground and excited states of many chemical systems.<br/><br/>However, my recent work reveals two fundamental failures of DFT and TDDFT in properly describing the electron density: size-dependent errors in electron ionization for DFT and lack of resonant charge transfer for TDDFT electron dynamics. I will present how both of these errors manifest in molecular systems, describe the density functional approximations that are responsible for each error, and show which methods will give more accurate electron densities.

Density-functional theory electron density errors in ionization and dynamics

251st National Meeting (2016)

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