Eur. Phys. J. B (2016) 89: 236
https://doi.org/10.1140/epjb/e2016-70110-y

Colloquium

Time-dependent density functional theory for charge-transfer dynamics: review of the causes of failure and success^*

Department of Physics and Astronomy, Hunter College and the Graduate Center of the City University of New York, 695 Park Avenue, New York 10065, USA

^a e-mail: johannafuks@gmail.com

Received: 23 February 2016
Published online: 2 November 2016

Abstract

The present study is an effort to unveil and characterize the failure and success of real-time Time-dependent density functional theory simulated charge transfer dynamics. To this aim, we study two distinct examples found in the literature: a dramatic failure is reported in [S. Raghunathan, M. Nest, J. Chem. Theor. Comput. 7, 2492 (2011)] whereas in [C.A. Rozzi et al., Nat. Commun. 4, 1602 (2013)] the simulations show good agreement with experiments. We find that the choice of Single Slater Determinant for the Kohn Sham initial state renders the simulation of charge transfer dynamics starting in the ground state very challenging. In contrast, starting the simulation in a photo-excited state facilitates the description and we show that even a simple functional can perform well. We formulate exact conditions to be satisfied by the exchange-correlation functional in order to keep the resonances of the system constant and relate the degree of their violation to the performance of a given functional approximation. We show that even the best possible ground state approximation to the exchange-correlation density functional violates the exact conditions, resulting in inaccurate dynamics.