Friday, November 26, 2021 -
12:30 to 13:30

Dear All,

We will have a seminar this Friday (26.11) from Dr. Gianluca Levi, Postdoctoral researcher at the Science Institute and Faculty of Physical Sciences, University of Iceland. The seminar will be streamed on Zoom, for more information see below.

When: Friday 26.11, 12:30-13:30

Where: Zoom,

Title: Excited-state and solvent dynamics during photoinduced molecular reactions in solution

Abstract: In order to design more efficient photocatalysts and solar energy conversion devices it is important to have an understanding of how nuclei and electrons respond to absorption of light. While modern time-resolved spectroscopy and X-ray scattering techniques can provide information on light-triggered transient electronic and structural changes of molecules in solutions, the interpretation and analysis of such experiments is complicated and relies to large extent on simulations of these ultrafast processes. Simulations of the photoinduced dynamics of a solvated molecular complex are challenging because they require calculations of excited electronic states and the corresponding motion of the atomic nuclei after absorption of a photon. One strategy is to treat the motion of the nuclei classically while computing energies and atomic forces on the fly using a quantum mechanical (QM) approach for the part of the system where the photoreaction is localized and classical potential functions based on molecular mechanics (MM) for the remaining solvent. QM/MM direct dynamics simulations of photoinduceed processes require a computationally affordable, robust, and reliable QM method to calculate excited states. I will illustrate our efforts to address these requirements by developing new excited-state methods within density functional theory based on finding saddle points of the energy as a function of the electronic degrees of freedom[1–3]. I will describe the challenges connected to this kind of calculations and the strategies that we have devised to overcome them. I will then show two examples of applications of our QM/MM direct dynamics methodology; one where the simulations helped the interpretation of femtosecond X-ray scattering experiments on a photocatalytic diplatinum complex in water performed at an X-ray free electron laser facility[4,5], and one where the simulations elucidated the debated photoinduced ligand flattening dynamics in a copper molecular photosensitizer and the interplay with the response of the solvent[6].

Hope to see all of you there!

Best wishes,

Pétur Orri Heiðarsson

Associate Professor

Science Institute

Department of Biochemistry

Askja- The Natural Sciences Building

University of Iceland

Sturlugata 7, 102 Reykjavík

Office +354 5254276


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