8. Theoretical soft matter physics
Soft matter physics is a rapidly developing field of research with a pronounced interdisciplinary character, re-uniting scientists from physics, chemistry and biology. Research of the group of Gerhard Kahl focuses on theoretical investigations on a particular subclass of soft matter systems, namely colloidal dispersions, i.e., mesoscopically sized particles (such as polymers, dendrimers, or microgels with a size ranging from 1 nm to 1 mm) immersed in a microscopic solvent (such as water).
In striking contrast to hard (i.e., atomic) systems the properties of colloidal dispersions can suitably be tailored: this is either achieved via modifications of the solvent or by well-defined strategies in the assembly process of the colloidal particles. This seemingly unlimited freedom to create new materials is also accessible to theoretical investigations. In fact, one of our goals is to assemble – in the sense of computational material sciences – colloidal particles that display desired structural, mechanical, rheological, ... properties. Classical computer simulations and statistical mechanics based concepts (such as density functional theory of liquid state theories) are highly efficient and reliable tools that allow to evaluate properties of macromolecules assembled on the computer.
Another remarkable feature of colloidal dispersions is their ability to selforganize in a large variety of ordered structures: micells, spirals, chains and layers, cluster phases or gyroid phases are a few examples. One key question from a theoretician’s point of view is the following: given some colloidal dispersion, how will the system solidify in an ordered structure. Over the past years a very efficient, reliable, and flexible optimization tool has been developed in our group, which is based on ideas of genetic algorithms (GAs). This search strategy uses features of evolutionary processes, such as survival of the fittest, recombination, or mutation. GAs have indeed brought along a break-through in solving above mentioned problem and have therefore become a highly appreciated tool in the community.
GAs can equally well be applied to bulk and surface problems of hard matter systems; we are therefore ready to share our experience with the groups of Blaha, Held, Mohn, and Redinger. On the other hand, the high degree of flexibility of GAs makes them an attractive tool to a widespread range of problems with possible applications in the other partner groups.