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Research Interests

Please also see my “Publications by Topic” page.

On the one hand, I am very active in developing methods. 20 of my publications (see list) are related to method development. I also implement many of these methods in freely available software packages. My C/C++ programming experience is more than 20 years.

On the other hand, I perform molecular dynamics simulations to study the structure and dy­namics of complex bulk phase systems such as mixtures, ionic liquids, membranes, and inter­faces. To do so, I use both ab initio molecular dynamics simulations (24 publications, see list) and force field molecular dynamics simulations (21 publications, see list).

I am convinced that particular scientific value lies in the collaboration between theoretically and experimentally working colleagues. I have published 22 articles together with experi­mental groups (see list). In many cases, we were able to complement or explain the experi­mental results with our simulations.


I am active in the following fields of scientific research:

Spectroscopy

Together with my co-workers, I am developing computational meth­ods in the field of vibrational spectroscopy, in particular for the prediction of bulk phase infrared, Raman, vibrational circular dichro­ism (VCD), Raman optical activity (ROA), and resonance Raman spec­tra from ab initio molecular dynamics (AIMD) simulat­ions. For exam­ple, we were the first to predict the ROA spectrum of a bulk phase system in 2017 (see article), and the resonance Raman spectrum of a bulk phase system in 2019 (see article).

Self Organization and Microheterogeneity

I was involved in many studies on self organization and micro­hetero­geneity in complex liquid systems. Those include lipid bilay­ers, deep-eutectic solvents (DES), mixtures of ionic liquids, and low-polarity water shells around TEMPO radicals. In 2015, I have developed the Voronoi-based domain analysis method, which en­ables to study microheterogeneity from MD simulations in great de­tail.

Free Energy Calculations

In my group, we explore the free energy profiles of processes and reactions under full solvent influence by using metadynamics. We have developed a new simulation protocol, called “HyAIMD” (Hy­brid AIMD), which effectively blocks unwanted side-reactions in AIMD-based metadynamics. With this approach, we were able to correctly predict the product ratio and selectivity of an enantiose­lective organo­catalytic aldol reaction in explicit solvent.

Interfaces and Ion Transport

I have contributed to several studies on solid state surfaces, liquid interfaces, and evaporation processes. I was involved in the EU-funded FP7 MODERN project, which aimed at modeling the toxicity of metal / metal oxide nanoparticles. I am experienced with comput­ing adsorption energies and entropies as well as electronic surface properties such as the band structure.

Furthermore, I contribute to the development of Markov models for proton and ion transport in solid state materials, allowing for the accurate description of these processes in inhomogeneous (non-ideal) systems up to the micrometer and microsecond scale. This is highly relevant for the research on new membrane materials for high temperature fuel cells or on solid electrolytes for batteries.

Ionic Liquids

I am interested in investigating the fascinating properties of ionic liquids, in particular their hydrogen bond network and their unique solubility properties. In my group, we study the dissolution of cel­lu­lose in ionic liquids. For example, we have established tria­zol­ium-based ionic liquids as a novel class of cellulose solvents. We also develop force fields for ionic liquids and their mixtures.

bqb Format

I am also active on the field of “big data”. In 2018, my colleague and me have developed a lossless compression algorithm for trajecto­ries of atom positions or volumetric data, which reaches a signifi­cantly higher compression ratio than any other existing method. In the case of volumetric data trajectories (such as electron density CUBE files), a lossless compression ra­tio of around 35 : 1 is reached.

Voronoi Integration

We have developed the Voronoi integration method, which gives molecular electromagnetic properties (such as dipole vector and quadrupole tensor) via integration of the total electron density on a grid. This approach is very useful for computing all different kinds of bulk phase vibrational spectra, as we have demonstrated for infrared, Raman, VCD, ROA, and resonance Raman spectra.

Based on the radical Voronoi tessellation, we have developed a method for computing optimized atomic partial charges (“Voronoi charges”) from AIMD. The radii are optimized on-the-fly to minimize the molecular and atomic charge fluctuations, so that the approach does not pos­sess any empirical parameters and yields a rigorous definition of atomic charges in the condensed phase.