Systems, where a fully atomistic treatment is not feasible, can be modelled as dissipative quantum systems coupled to a classical environment. Time-dependent properties and observables such as spectra can then be obtained from the evolution of the reduced density matrix.
A versatile method for the time-dependent simulation of such systems is the Quasi-Adiabatic propagator Path Integral (QUAPI) approach. We develope a powerful parallel implementation of QUAPI including further methodological advances that allow to speed up simulations by several orders of magnitude. This is achieved by Mask Assisted Coarse Graining of the Influence Coefficients (MACGIC-QUAPI) and inclusion of low scaling sorting and merging algorithms in on-the-fly path selection.
The MACGIC-QUAPI method successfully interpolates between different regimes of excitation energy and electron transfer. It can be applied to large systems like a fully coupled 24-state Fenna-Mathews-Olsen complex and converges to the exact results as comparison to high-level hierarchical equations of motion calculations reveals. Furthermore, the algorithmic structure allows for efficient parallelization on modern high-performance computing hardware.
Further information: M. Richter, Benjamin P. Fingerhut J. Chem. Phys., 146, 214101 (2017)
Simulation of 2D Spectra
Nonlinear 2D spectra of molecular systems in the UV-Vis spectral region can be simulated from atomistic molecular dynamics trajectories subject to non-adiabatic relaxation. To achieve this, the nonlinear exciton propagation protocol, that relies on a quasiparticle approach, is combined with the surface hopping methodology to account for quantum-classical feedback during the dynamics. Phenomena like dynamic Stokes shift due to nuclear relaxation, spectral diffusion and population transfer among electronic states are thus naturally included. The algorithm can be applied to a variety of systems ranging from simple two-state models to complex organic molecules like the bichromophore diphenylmethane.
Further information: M. Richter, Benjamin P. Fingerhut J. Chem. Theory Comput., 12, 3284-3294 (2016)
Molecular Dynamics with Surface Hopping in the Adiabatic Representation Including Arbitrary Couplings
Semiclassical surface-hopping methods can be modified to treat arbitrary couplings in molecular systems including all degrees of freedom. A reformulation of the standard surface-hopping scheme in terms of a unitary transformation matrix allows for the description of interactions like spin-orbit coupling or transitions induced by laser fields.
M. Richter, P. Marquetand, J. González-Vázquez, I. Sola, and L. González J. Chem. Theory Comput., 7, 1253-1258, (2011)
S. Mai, M. Richter, M. Heindl, M. F. S. J. Menger, A. Atkins, M. Ruckenbauer, F. Plasser, M. Oppel, P. Marquetand, L. González SHARC2.0: Surface Hopping Including Arbitrary Couplings - Program Package for Non-Adiabatic Dynamics, sharc-md.org (2018)
Image: Martin Richter
since 09/2018: Postdoc with Prof. S. Gräfe, Friedrich Schiller University, Jena, Germany
11/2014 - 08/2018: Postdoc in the Junior Group Biomolecular Dynamics (group leader: Dr. B. P. Fingerhut), Max Born Institute, Berlin, Germany
2015 Loschmidt Award of the Austrian Chemical Physical Society
10/2010 - 10/2014: PhD Thesis with Prof. L. González 'Femtosecond dynamics of DNA/RNA nucleobases after UV excitation including spin-orbit couplings', Friedrich Schiller University, Jena, Germany (10/2010 - 06/2013) and University of Vienna, Vienna, Austria (07/2013- 10/2014)
01/2010 - 09/2010: Diploma Thesis 'Semiclassical molecular dynamics including spin-orbit coupling and field induced state hopping', Friedrich Schiller University, Jena, Germany