Computer models for chemical reactions

How do atomic nuclei move around in molecules? And how does this lead to changes in their chemical structure? And to reactions? These are the kinds of questions addressed by Professor Benjamin Fingerhut. A newcomer to LMU, he uses quantum mechanical computer models to simulate “ultra-fast dynamics”. His work is thus focused on the quantum level: the level of the very tiniest physical entities. “Our questions have their roots in chemistry, but to some extent the methods come from physics.”

Having studied chemistry at LMU, Fingerhut earned his doctorate here too in 2011. His doctoral thesis involved developing an algorithm to model biomolecular electron transfer reactions – in the reaction centers (RCs) of photosynthetic bacteria, for example. Under a Feodor Lynen Scholarship from the Humboldt Foundation, he then did two years’ postdoctoral research at the University of California in Irvine, where he applied himself to the theoretical description of spectroscopic methods. In early 2014, he moved to the Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy in Berlin. Here, Fingerhut set up the Emmy Noether junior research group and was given an ERC Starting Grant. Since last summer, he has been researching biomolecular dynamics as Professor of Theoretical Chemistry at LMU.

Processes in the femtosecond to picosecond range

The basic issue that repeatedly preoccupies him in ever new ways is “ultra-fast dynamics in the condensed phase”. “These are the dynamics that occur on the elemental timescale of nuclear energy,” he explains. “We want to understand how atomic nuclei move in reactive molecules and how these dynamics lead to relevant chemical processes.” These processes unfold in the femtosecond to picosecond range of 10-15 or 10-12 seconds respectively and can these days be tracked in real time with the aid of laser spectroscopy. “The molecule is excited by the laser, and we watch how it interacts with its environment,” Fingerhut says. That said, the chemist is less interested in isolated, “free-floating” molecules and more in the “condensed phase”, i.e. the liquid or solid state of aggregation. “Ultimately, we want to understand the underlying quantum system and how it interacts with its environment.”

Fingerhut simulates this kind of reaction in theoretical models on the computer and compares them with the experimental observations of his research partners. “Very, very powerful computers” are needed to do calculations based on the algorithm his team has developed, he says. Right now, he adds, the team is “toying” with the science of whether artificial intelligence could speed up Benjamin Fingerhut’s calculations.

His numeric models have all kinds of scientific applications. “One involves researching the fundamental dynamics of photosynthesis, where photons are absorbed and their energy is put to good use in what is known as a light-harvesting complex.” Using the professor’s method, this and the ensuing temporal dynamics of electron transfer between molecules can be simulated exactly. In Berlin, Fingerhut had previously also researched the boundaries between deoxyribonucleic acid (DNA)/ribonucleic acid (RNA), surrounding water and embedded ions. “The question in this context was: What is the influence on the structure and stability of a strand of DNA or RNA? How could we dock onto it?”

“Qubits have a similar set-up”

For Fingerhut, Munich was an attractive proposition not least due to the number of network links that exist for his group both at LMU and beyond. In the context of TUM and LMU’s e‑conversion cluster, for example, he collaborates with LMU researchers Ivana Ivanović-Burmazović, Professor of Bioorganic Chemistry and Coordination Chemistry, and experimental physicist Professor Tim Liedl. “And there are lots of extremely interesting new appointments from our perspective,” he adds. As a scientist, he says, you feel that you are in good hands in Munich.

What the chemist particularly likes about teaching at LMU is having a body of students “who are not afraid to challenge the professors with their questions” and who engage them in discussion. “There are some bright minds among them from whom we will one day be able to recruit very good junior researchers.” In his own corner of academia, Fingerhut also has plans to tackle quantum technologies going forward. “Qubits – the quantum systems on which quantum computers are based – have a similar set-up to the ultra-fast dynamics we see in the condensed phase.” Even for elementary qubit entities, he confesses the urge to understand “how the environment contributes to their dephasing and relaxation, i.e. the return to their initial energetic state”.