Optimally-tuned range-separated density functionals

People

Project coordinator: Sergey Bokarev
Co-workers: Olga Bokareva, Gilbert Grell, Tobias Möhle

Project description

Many practical problems relevant for photovoltaics and photocatalysis involve a long-range electron relay initiated by the absorption of light. Often the separation of charges starts from the excitation to the so called charge transfer (CT) states. However, description of such states poses rather strict demands to a theoretical method. Unfortunately, the density functional theory, although being very efficient and reasonably accurate for many applications, is not reliable for the CT states due to a fundamental deficiency of the exchange part of standard approximate functionals at long ranges. To overcome this drawback, a trick is to separate the short- and long-range parts and utilize the exact (Hartree-Fock) exchange for the latter region. The details of this separation, e.g. a speed of switch between short and long ranges, are density- and thus system-dependent and ideally need to be chosen on a case-to-case basis. To do so, we apply an automated fully ab initio self-consistent procedure to optimize range-separation parameters and thus improve the description of photophysical and photochemical properties of photoactive molecules. Remarkably, the optimal tuning of the density functional also improves the ionization potentials and hence is applied in theoretical photoelectron spectroscopy.

Publications

  1. O. S. Bokareva, G. Grell, S. I. Bokarev, O. Kühn
    Tuning Range-Separated Density Functional Theory for Photocatalytic Water Splitting Systems
    J. Chem. Theory and Comp. 11, 1700 (2015)
  2. S. I. Bokarev, O. S. Bokareva, O. Kühn
    A Theoretical Perspective on Charge Transfer in Photocatalysis. The Example of Ir-based Systems
    Coord. Chem. Rev.
    304-305, 133 (2015)