The general theme of our research consists in understanding structure, dynamics, and chemical reactions of complex molecular many-body systems - bridging the gap between chemistry and physics. Our aim is to capture nature as closely as possible by theoretical means - the basic entities being nuclei and electrons. This implies that we have to use atomistic ab initio computer simulation techniques which are capable of including dynamics and quantum mechanics - of course only approximatively. The notion "ab initio" or "first principles" means for us that we neither want to fit to experimental data nor do we want to adjust any parameters. The central working horse to turn these ideas into practical numerical tools are in particular the ab initio simulation methods going back to ideas of Car and Parrinello (1985).

The crucial idea of the Car-Parrinello approach to ab initio molecular dynamics consists in efficiently solving the electronic structure problem "on the fly" as the molecular dynamics trajectory is generated for a set of classical nuclei using Newtonian mechanics. Thus, within ab initio simulations it is neither required to compute a high-dimensional global potential energy surface prior to the simulation, nor is it necessary to reconstruct it approximately from local pair (or few-body) interactions.

This "classical" Car-Parrinello approach has been extended by Marx and Parrinello (1994) to include also the nuclei as quantum-mechanical degrees of freedom. In order to achieve this for "large systems" composed of the order of 100 nuclei or more, the Feynman-Kac formulation of quantum statistical mechanics in terms of path integrals is employed. This class of fully quantum-mechanical ab initio path integral techniques makes it possible to study - in a time-averaged sense - zero-point motion and tunneling effects for instance of protons in hydrogen-bonded or other complex environments.

More recently, another extension of the original Car-Parrinello method, which assumed the electrons to stay in the electronic ground state, was developed by Doltsinis and Marx (2002). The basic idea of this nonadiabatic ab initio dynamics technique is to use Tully's surface hopping algorithm in combination with the so-called restricted open-shell Kohn-Sham Ansatz. This efficient approach "beyond the Born-Oppenheimer approximation" allows us to study photochemical reactions with particular focus on laser-induced processes in solution.

These simulation algorithms together with the required computer hardware constitute what we like to call a "Virtual Laboratory". In this theoretician's version of a real laboratory chemical reactions of molecules can take place at finite temperature in liquids or on surfaces - solely governed by the basic laws of physics. This makes it possible to investigate "chemically complex" molecular systems - possibly in close contact with experimentalists. To foster this, the Marx Group is or has been involved in several large-scale collaborative research projects such as SFB 558 ("Heterogeneous Catalysis"), FOR 436 ("Water at Interfaces"), FOR 618 ("Molecular Aggregation") and various Projects of the Volkswagen-Stiftung ("Stress-Controlled Molecular Electronics", "Multiscale Modelling").

Much more detail on this topic can be found in the monograph
"Ab Initio Molecular Dynamics: Basic Theory and Advanced Methods"
written by Dominik Marx and Jürg Hutter
(Cambridge University Press, Cambridge 2009)

The research group itself consists (as a time average) of physicists, chemists, and biochemists and it is characterized by trans-disciplinarity. The spectral range of our interests is rather broad and covers applications to molecules, clusters, liquids, solids, surfaces, as well as to biologically relevant species. In order to be able to achieve these goals, we are constantly developing novel techniques and/or we are improving existing methods.

If you want to know more about the various ab initio simulation techniques used and developed in the Marx group and applications of these methods we recommend to have a look at our local collection of books and review articles on the subject.

The publication lists of Dominik Marx and the Marx Group can be obtained as a pdf file (CV of Professor Marx). Note that it is illegal to download most of the articles listed there: please contact us at theochem@theochem.rub.de and you will receive legal reprints as soon as possible.