Stuttgart 2012 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 18: Molecular Dynamics

MO 18.5: Vortrag

Donnerstag, 15. März 2012, 15:15–15:30, V38.02

Multi reference perturbation theory for non-adiabatic on-the-fly molecular dynamics: implementation and benchmarking — •Sven Oesterling, Artur Nenov, Benjamin P. Fingerhut, and Regina de Vivie-Riedle — Ludwig Maximilians Universität München, Department Chemie

Semiclassical on-the-fly dynamics provide a way to simulate molecular processes of moderate sized systems. Treating the nuclei classically, abolishes the need to precompute potential energy surfaces, and thus allows for a full dimensional treatment of the molecular degrees of freedom. The electronic properties are computed with quantum chemical methods, adequate for system-size and nature of the problem. Regarding excited states, major challenges are the accurate, yet cost efficient calculation of the electron correlation, and the precise description of non-adiabatic events. The complete active space perturbation theory (CASPT2) has been shown to resolve the correlation issue, yielding excitation energies close to experimental values.

We implemented an interface for the CASPT2 method, included in the Molpro quantum chemistry package, in the Newton-X dynamics package. As there are no analytical non-adiabatic coupling vectors available in common quantum chemistry programs, a numerical approach, suggested by Tao et al., was used to compute the coupling. The implementation is benchmarked with ethylene, with additional focus on the relevance of Rydberg-states.