Our research is concerned with the development and application of quantum-chemistry methods applicable for medium-sized systems consisting of up to several hundred atoms. One important ansatz is frozen-density embedding (FDE) [1], in which the total system, consisting of one or more ‘’active’’ molecules and dozens of environment molecules, is partitioned into subsystems, which can be treated separately. This leads to significant reduction in computation time so that the sampling of snapshots becomes available for increased system sizes. The implementation of the new methods is carried out in the in-house program package KOALA [2].

The KOALA program

  • DFT methods: gradients, TDDFT
  • Coupled-cluster methods: time-independent and time-dependent properties
  • Efficient methods: density fitting
  • Frozen-density embedding (FDE)
  • Continuum solvation models
  • OpenMP parallelization
  • Publications which include results
    obtained using KOALA: 11

The newly developed methods have been employed to study different chemical problems, including absorption spectra of ligands in solution [3], the investigation of relaxed excited states [4] or biologically active chromophores in protein environments [5]. The FDE ansatz is not only favorable in terms of efficiency but also leads to molecular properties that are intrinsically localized to the subsystems, facilitating a chemical interpretation. In order to be able to describe properties arising due to an interaction of the molecules, it is possible to compute coupling matrix elements in an additional coupling step [6].


Computing UV/vis spectra using a combined molecular dynamics and quantum chemistry approach: bis-triazin-pyridine (BTP) ligands studied in solution [3]

Analytical Nuclear Excited-State Gradients for the Second-Order Approximate Coupled-Cluster Singles and Doubles (CC2) Method Employing Uncoupled Frozen-Density Embedding [4]

Communication: Biological applications of coupled-cluster frozen-density embedding [5]

Wave-function frozen-density embedding: Coupled excitations [6]


Selected Publications

  1. S. Höfener, A. S. P. Gomes, L. Visscher, J. Chem. Phys. 136, 044104 (2012)
  2. S. Höfener, J. Comput. Chem. 35, 1716 (2014)
  3. S. Höfener, M. Trumm, C. Koke, J. Heuser, U. Ekström, A. Skerencak-Frech, B. Schimmelpfennig, P. J. Panak, Phys. Chem. Chem. Phys. 18, 7728 (2016)
  4. J. Heuser, S. Höfener, J. Chem. Theory Comput. 14, 4616 (2018)
  5. J. Heuser, S. Höfener, J. Chem. Phys. 148, 141101 (2018)
    DOI: 10.1063/1.5026651
  6. S. Höfener, L. Visscher, J. Chem. Theory Comput. 12, 549 (2016)