VSC School Seminar: Molecular Photodynamics Simulations on HPC Systems
Many areas of current research, such as photovoltaics, photobiology, and phototherapy are characterized by ultrafast processes in the excited state manifold. The computational description of such processes requires explicit dynamical simulations of the nuclear and electronic degrees of freedom, as well as their interplay. Here, on-the-fly surface hopping dynamics offer themselves as an attractive option as they allow to simulate dynamical processes without any bias toward specific nuclear degrees of freedom while still incorporating essential quantum effects. Despite the high potential of these simulations, the computational effort spent becomes a limiting factor, and high-performance computing (HPC) becomes imperative for many applications of current interest. The dynamics simulations require the computation of different terms related to the electronic energy, the nuclear forces, and nonadiabatic state-to-state interactions. Depending on the molecular system studied and the computational infrastructure used, either one of these steps may act as the computational bottleneck. This heterogeneity of the computational steps causes severe challenges for the dynamics simulations as the different computational steps have to be optimized individually.
In this talk, first the field of photodynamics and applications in our group are reviewed. Subsequently, specific method developments carried out within the VSC School Project "Parallelizing the Gradient and Overlap Calculation for MRCI Wavefunctions on HPC Clusters" are discussed. A major achievement is concerned with the development of a flexible and highly efficient code of the computation of wavefunction overlaps . This code was implemented to compute nonadiabatic interaction terms for the multi-reference configuration interaction method and has been extended to various other electronic structure methods. After presenting the technical details of the implementation, a number of high-profile applications currently on their way on the VSC are presented. Due to the flexibility of the developed code, also other application areas have been explored, such as the comparison of general many-electron wavefunctions  and the computation of Dyson orbitals. Methods for the computation of atomic forces will be discussed, as well. In this case progress, that has been achieved in- and outside of this project, is explained in detail.
This talk is based on work supported by the VSC Research Center funded by the Austrian Federal Ministry of Science, Research and Economy (bmwfw).
 Plasser, F.; Ruckenbauer, M.; Mai, S.; Oppel, M.; Marquetand, P.; González, L.;
J. Chem. Theory Comput., 2016, 12, 1207.
 Plasser, F.; González, L.; J. Chem. Phys., 2016, 145, 021103.
Department of Theoretical Chemistry, University of Vienna
Date, Time, and Location (NEW TIME, NEW LOCATION):
20.01.2017, 15:00 - 17:00, FH Hörsaal 7 (TU Wien, Wiedner Hauptstraße 8-10, 2nd floor, yellow area)
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The course material is available for registered attendees only.
The presentation was also available as a livestream.
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